dunno what level you are but here's a simple class to work towards.
Scar silenced & extended mags if you have it
Mp9 silenced if you have Blind Eye Pro, SMAW or Stinger if you only have Blind Eye.
Blind eye pro
Assassin pro
Dead Silence (Marksman if you don't have it)
Portable Radar (high level so you may not have it)
Betty
Specialist package
Scavenger
Sleight of hand
Hardline
This setup protects you from every killstreak assuming you're not near a teammate and keeps you silent as possible. Scar is insanely accurate and powerful. Very good at most ranges. You can work your way around fairly safely. after 2 kills, not worry about ammo or other guns, after 4 you can be a little aggressive. After 7 you're a beast. If you have Blind Eye Pro you can take a killstreak down with your silenced gun quickly, without showing up on radar, so get it to Pro! With Scavenger at 2 kills, and downing killstreaks counting as a kill, you can take something down with bullets, kill one guy and have Scavenger pack waiting for you.
Thing about specialist is this. Although you can get all perks before you've even unlocked them, it doesn't give Pro versions until you earn them. Blast shield pro isn't the greatest, but once you get up to 7 kills people want to take you down and that extra grenade and flash protection is awesome! So get blast shield to pro.