@WillMidz, to be honest, ive got a silly amount of guns, prob 6 or 7 shotguns, prob 5 or 6 snipers, maybe 7 or 8 bullpups, 8 pistols i think, & prob another 15 to 20 of various m4's, G36's, m60, M14's, AK's, aug, VSS, FAL, G3, FNC & prob some I've forgotten.
I have favourites, such as my cyma M14 socom, but to be honest for a first gun I'd definitely recommend something that takes stanag mags, that way when you buy a back up rifle, there's a lot to choose from that should take the same mags, definitely will make life easier for changing guns mid gameday & your pouch setup.
What to pick, most brands are pretty good quality nowadays, it's as much about what you like the look of ??