I agree with Chaz. I played both paintball and airsoft. Both are completely different.
If you are on a budget. Forget the optics, and pistol. If you want to do Milsim, get a good vest, hydration, get a better rifle and better mags. Try to buy once if you can. You can always add a pistol later.
I run only iron sights, but do use a red dot for indoor games.