RS Type 56 or Daytonagun if you want the blowback action (be warned these things can easily go for $2000+ in Canada).
You don't really need upgrades if you go with the RS Type56, you can just game it out of the box, they're that good. Not to mention any upgrades you do put into it won't improve it by that much.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE