I have a crazy fast trigger finger, so I use FN FAL dual mag and CZ75 extended mag with scavenger pro (I run around the map a lot), Hardened pro (keeps my aim on when I get hit), and Second Chance Pro (Spam handgun with 18 shots FTW, getting revived saves killstreaks)
Trick for Second Chance: If they go behind a wall after downing you, shoot like 1 or 2 shots then stop. They think you ran out, pop out for easy kill, boom they're dead.
As for killstreaks, I go 3, 5, 8. Spy plane tells me where to run, I like the randomness of care packages, and Blackbird is just FTW.