I'd suggest a m4 too, great all purpose platform and G36 mags are a pain to fit into vests. Whatever you choose, if you go with same platform, you can share mags. You can run scopes on any rifle platform anyways, may look silly but it'll work
BTW, HackD is sharing good wisdom, don't need to be fully fitted out for your first game. I found that you'll figure out what you're lacking when you've experienced it. Not to say you shouldn't buy proper eye protection and boots, those are a must!