So yeah CSGO is a decent game
UNLESS SPECIFIED OTHERWISE, EVERYTHING HERE IS REFERENCING DUST 2

I'm at Master Guardian right now, and it's pretty tight

anyways, I've found that oddly enough, my best build is actually

Default Pistol
Full Armor
MP7
Flash
Smoke
Decoy

It's a really cheap loadout, and maybe if you skimp on the grenade, the armor and mp7 alone should be around 2700, which is cheaper than most rifles CT side. It also gives you the opportunity to move, and the mp7 is about a 4-5 shot kill at medium, and a 2-3 HS. However, the recoil spread when moving is very generous, so I just run around players and since it kicks straight up, I aim at their stomachs and get headshots like mad. I can play extremely aggressively and I love that, and the decoy makes up for my lack of firepower.

For example, when defending on Dust after a plant, I can throw the decoy into the crates around B when I hear guys coming from dark, and they'll assume i'm prefiring when in reality i'm right next to them.

Probably my favorite thing to do when on the offensive though, is to find a chokepoint very early and rush there with my mp7, and then smoke it off, shoot through the smoke, drop a decoy at my feet, shoot some more and leave. The guys on the other end of the smoke keep shooting through it, and I can actually run around and flank, since I can shoot on the move.

Even at range the mp7 is great. What I've noticed a lot about players at range, is that especially with the AK, everybody is so focused on getting headshots and moving accuraccy is so bad, that either they'll get the HS or deal 0 damage. What I do is strafe a lot and just put rounds downrange, and although doing like, 17 damage per shot is pretty bad, actually landing like, 10 of them really works.

I can't tell you how many times I've cleared out dark around B just by peeking the hallway and firing blindly into the group over and over again, and just connecting shots really quickly instead of missing like the AK would


EDIT
Also, this kit is so damn cheap that if I play T, and we get a plant on first round, I can afford this shit by round 2, which is awesome. Also, mid and later game I'll have so much money left over that I end up dropping AWPs for my team, and at the end of every round I'll drop my MP7 and find the nearest AK/AWP/Auto and just drop it to someone next round, since re-buying the MP7 is so cheap