N18 New player- how is my orlock gang loadout?

If you are going to play skirmishes , I'd swap the captain's skills for something more suitable. Fixer and Too Pretty for Prime are for campaign play, where collecting credits between games has more meaning. Maybe Mutioneer to help with the difficult ammo checks. Melta part of the combi-weapon seems a bit overkill, but if your friends are planning to bring brutes, it'll have its use.

The plasmagunner would benefit from telescopic sight. You could drop the autoguns from the two gangers to afford it.

Arms Master has a decent BS, he/she would do good for having a shotgun, while moving to the hammer strike distance. No idea where you could take the credits for it though.
 
If you are going to play skirmishes , I'd swap the captain's skills for something more suitable. Fixer and Too Pretty for Prime are for campaign play, where collecting credits between games has more meaning. Maybe Mutioneer to help with the difficult ammo checks.
I agree with @Sump Thing on skills. Fixer and Too pretty for Primus are good campaign skills not for skirmishes.

You did say the aim was for campaigns so I'll go from there
There is an argument that Combi weapons jam or unload both profiles on a failed ammo check. (It states in the rules accept the worst result. Which would be both profiles becoming Out of Ammo. GW should have either put a worked through example in the Combi rules to clarify or just wrote "apply the worst result for that profile". Three little words that would make it clear. They even go on to say how the two profiles are tracked separately so that is what they intended. Three words).
Anyway that Combi point aside I have a few issues with the combi bolter myself. The high 6+ ammo roll for the bolter is punishing with combi. Every 6 shots, on average, you roll a Ammo Symbol then need a ammo check which you then need to roll a double six to avoid jamming the bolter. To reload it you then need to roll two sixes again to pass the Ammo check to reload. That is very chancy. The melta profile also has scarce so again every six shots on average you then need to roll two 4+s and if you fail you can't use the gun for the rest of the game. Instead of a 50% chance of success you cut it down to a 25%. You would be better off buying the two weapons separately in my opinion.
It only costs 15 credits more that way and you avoid the quite real risk of spending all game feverishly trying to reload your top damage dealers gun.
 
Your Sergeant has a good solid loadout. Plasma rules. Get a sight later to make it even better.
Your Arms master has good WS and BS so is geared to both melee and shooting either is a good option but to start with I would pick one and focus on that for a few games untill you have the credits to fill in the other role at a later point. The Arc hammer is great for smashing and Nerves of steel is a good skill for getting into combat. I would not bother to give him a stubgun. Just save the credits either for a more punchy pistol from the Trade Post later, nothing is wrong with the stubgun but it will seem a bit lackluster compared to your Hammer for those times when you sneak a shot off when out of melee range. You also have Basic weapon access and primary skill access, i.e a easier access to choosing a skill over random selection, and the Bravado skill tree with Shotgun Savant. There is a lot of options for shotgun and with that skill it adds a lot of punch to a already good range of Basis weapons.

Like your wreaker load outs. The Flails are great in wreckers, other gang fighters too. The duel stubguns, sawn off shotgun and demo charge may not be a power gamer choice but they are just too cool. The gunslinger wreaker will need to get close to use twin guns blazing and so will the demo charge one but getting there is no problem with the jump boosters. Surviving retaliation can be tricky and a unlucky scattering demo charge, which is also unstable when jump boosting, can be hazardous but wreckers are just plain bonkers and fun.
The sawn off shotgun needs the solid shot. With the sawn off, again just looks super cool, you have to get awfully close so you need the punch to make a dent.
I would drop the autoguns on your gangers. Your combat shotgun and grenade launcher are great enough that they don't need back ups. Just upgrade the shotgun with firestorm ammo later to improve it as your gang progresses. For your grenade launcher get smoke grenades as quickly as possible, sadly from Trade Post as you can't start with them so after your first game, the Smoke effect is great for providing cover on its own and it has a 4+ ammo roll as well. When your 6+ frag or Krak grenades are Out Of Ammo the whole launcher is but you can reload it using any ammo types you have and each ammk type is reload. So when your frags jam the launcher you only need a 4+ to reload not a 6+.
 
Some General necromunda points for a new player. Take a good look at the missions crew sizes you play. Most have crews of up to ten for the balanced mission. Make an assumption that 2-3 fighters will be in recovery every game. Add a couple more for good measure and your running campaign campaign roster should be around 15 gang members plus and hangers on and brutes. Any more and you spread your funds and combat experience too thin.

Four champions/leader is a good aim as a minimum.
You will need one to do a post battle Trade action, one will probably be in recovery and one will need to be available for a emergency Medical Escort actions. Having a extra one for A buffer is better for safety. The extra big guns/melee weapon are not ever a bad thing.
Rouge Docs are your friend. Get them early.
Heavy flamers are garbage. As is Flack armour.
Don't be afraid to bravely run away when the going gets tough. Better to have less deaths then fall into a death spiral.
The dice gods will smite you. Just take it in the chin and carry on. For every unstable plasma gun blowing up you get a juve who survives a four story drop.
 
There is an argument that Combi weapons jam or unload both profiles on a failed ammo check. (It states in the rules accept the worst result. Which would be both profiles becoming Out of Ammo. GW should have either put a worked through example in the Combi rules to clarify or just wrote "apply the worst result for that profile". Three little words that would make it clear. They even go on to say how the two profiles are tracked separately so that is what they intended. Three words).
GW did fix the combi -weapon trait. In the current rule book it writes "...ammo for the two parts of the combi-weapon are tracked separately - if one profile runs out of ammo, the other can still fire, unless it has run out of ammo." But I do agree that combis tend to run out of ammo sooner rather than later. The trick is to play Proper Preparation -tactics card on the wielder. This way the bolter part gets Plentiful, and the melta part loses the Scarce trait. Should the captain now have the mutioneer skill, it would greatly help to reload the ammo 4+ melta part.
 
Your combat shotgun and grenade launcher are great enough that they don't need back ups. Just upgrade the shotgun with firestorm ammo later to improve it as your gang progresses. For your grenade launcher get smoke grenades as quickly as possible, sadly from Trade Post as you can't start with them so after your first game, the Smoke effect is great for providing cover on its own and it has a 4+ ammo roll as well. When your 6+ frag or Krak grenades are Out Of Ammo the whole launcher is but you can reload it using any ammo types you have and each ammk type is reload. So when your frags jam the launcher you only need a 4+ to reload not a 6+.
Unfortunately in the current rule book the special ammo is listed under weapon profiles, and not in the wargear like in the old rulebook. Since gangers and specialists can only take weapons from their own list, most special ammo is off limits for them (they still get dumdums). It's kind of a no brainier, orlocks could otherwise get a horde of very cheap heavy flamers without Unwieldy, and with the Bullet Merchant hanger-on (25 creds for orlocks), the firestorm ammo would swap Limited to Scarce -trait too. Absolute fondue. Same goes for the grenade launcher and its smokes, off limits for orlock specs.
 
GW did fix the combi -weapon trait. In the current rule book it writes "...ammo for the two parts of the combi-weapon are tracked separately - if one profile runs out of ammo, the other can still fire, unless it has run out of ammo."
They have not changed the combi rules. The line you quoted has remained the same and shows the intent. My problem is with the line "When making an Ammo test for either of the weapons, roll twice and apply the worst result." The worst result for the weapon, which is described as a single weapon with two profiles not two separate weapons (" A Combi-weapon has two profiles"), is that the whole weapon jams/runs out of ammo.
In the rules for ammo checks they do state it is not always running out of ammunition it can be weapon jams as well.
In the section you quoted it specifically says ammo, lower case, is tracked separately. If they used the word Ammo, case it would be clear that it applies to the status of Ammo in regards to Ammo Checks rather than the physical rounds. So the rule says you track the bullets separately not the Ammo check value.

It is still a poorly written rule subject to a lot of word and definition confusion. When they state it is a single weapon with two profiles they later refer to it as "either of the weapons" marking it a plural not a singular. Then later they say the ammo is tracked separately and links that to the word profile again making it a singular.
Is it a single weapon with two profiles or a pair of weapons with linked profiles? GW as written say it is both!
It would not take much ink to clear it up.
For my first quote all they need to do is replace "weapons" with profiles of, which adds a single letter and at the end of my first quote add "for that profile' which is 14 letters.
For a mere 15 letters that Combi rules would read far better.

It also does not help that they use Ammo as a status, in regards to Ammo Check, and ammo as a physical object, as in say Firestorm ammo.
 
Unfortunately in the current rule book the special ammo is listed under weapon profiles, and not in the wargear like in the old rulebook. Since gangers and specialists can only take weapons from their own list, most special ammo is off limits for them (they still get dumdums).
Again unclear wording and formatting on GWs part.
In the Distribution Equipment step in the campaign section in the core rule book. It states "Any equipment currently held in the gang's Stash can now be distributed among it's models. Weapon choices must respect any restrictions noted in that model's entry in thier gang list."
Firstly "Any" then "respect any restrictions". That alone contradicts itself. They should say "The equipment" instead of "Any Equipment". That would clear that contradiction nicely.
Secondly in the Core rule book. They don't in the text make a distinction between weapons and ammunition which is basic sense. (GW lacking basic sense who would have thought...) However in the new tables the weapon and ammo types have separate entries and individual costs now along with rarity. The table clearly distinguishes between the weapon and the ammo types with the separate cost entries. So in the core rule book GW says both they are weapons and they are ammunition.
"He was shot?. No somebody threw it at him."
Thirdly in the House of books where they restrict gangers in weapons the specifically state "no restrictions upon the types of weapon they can take from this list, all weapon types within this list become available".
The use of lower case "weapon" and "type" makes it a generic term over a specific one. Take for example the word Conservative verses conservative. (Or say Republican or republican if you are say from the USA). One is a specific political party in the UK, the capitalised one, the lower case one is a more generic term. You get republicans, lower case, that would be appealed on what the Republican US party is and support say the Ancient Roman style republic style of government.
Using strictly the wording and grammar used in the House of ... Books it says that a specialist Gunner has access to the generic weapon type of grenade launcher as it uses lower case as opposed to if they used Upper case then it would specifically mean only the Orlock produced Grenade launcher but they did not.
Again GW don't think things through. They give multiple contradictions.
 
Thank you all for your help! Hopefully once I've played a few games I will be able to envision how all the rules and ammo checks and stuff work together so i have a better idea of what will work well for my orlocks. I'm just looking to use fun weapons and make some wacky plays hopefully :D.