Well, first some information about yourself?
How old are you? (answer is either 18+ or not 18+)
What country are you in?
If you keep moving the goalpost, the amount you're willing to pay, even as you are educated, you may never pin anything down.
Do you need an automatic weapon?
Do you intend to actually play airsoft?
I played my first 4 skirmishes without an automatic weapon, I have to say, with CQC at least it really is not needed - and often barred.
How large is the area you intend to play in, if under 30-40m I would recommend a Tokyo Marui Glock 17 Gas Blowback Pistol.
They're around £120 (with 1 mag). Gas is around £10 for 50-75 mag fills @ at least 35 shots per fill).
After that you need only silicone gun oil £5, BBs £5, eye protection £25. Extra magazines are £25 for 26rd and £35 for 50rd.