He can't use the M416 and even though that's one of my favorite weapons it's pretty expensive. Honestly just use the M4. You're several ranks and a lot of exp away from the Reflexive scope but once you get that each weapon is totally different. Wait it out. Put an itech on a ak74 and go pawn. Some of the cheapest weapons can be the best. Don't know really what style you play but if you're a camper you want a 2 shot killer. If you like to run around and rush you want a very light weapon that fires fast. So if you like camping you could always stick with the ak family of weapons or a g36 and if you like rushing the p90 works. You really have some shitty weapons right now.
No one can tell you which is the best gun for you, it all depends on how you play. You like close quarters then go for MP7, UMP or shotgun, want just an AR then go for M4A1 or M416, like sniping then either L9 or a semi auto. People can give you their opinions on guns like what's the most accurate and what has the least recoil etc but the best gun for you can only be answered by you.