Well, a few tips then:
Try to stay away for the open terrain, move along walls and objects, hide to recharge after a kill (if you can) you're an easy target there, use cloak in a smart way, only to cross open spaced or to approach undetected, also don't assume you're totally invisible, just a lot less but experienced players will pick you out easy.
Also, never stay on the same place for too long and keep moving, even when you're out of energy. Use armor only when in a face to face gunfight, it's pretty useless in other situations, especially because using it lights you up like a Christmas tree, so it makes you an even easier target for players that are far away, and it consumes energy.
Pick out a smart load-out, one that does well and is used by almost all the 'good' players is the Feline SMG, Nova or Hammer handgun, frag grenade and for the modules: Nano recharge (only getting useful starting at level II) or Energy Transfer (a level III must have for intense IA games), the other armor modules are total crap. Take Stealth Enhance, it's an absolute must or you will constantly run out of energy when things get tricky (or Blind Spot when you wanne snipe, otherwise you're too easily pinned down) and then for the power modules, take 'Mobility Enhance' if you want to move around cloaked a lot, use 'weapon pro' when you feel like you are always running out of bullets.
As for the weapons, use the SCAR or the Feline, or even the Jackal shotgun, a really good short range blaster for the beginner.
Good luck mate!