My advice re: guns is, before you buy your own, try skirmishing with an M4 or M16, AK47 or 74, a G36c or k and a bullpup of some sort, L85 or Steyr AUG say. That way you'll get a good idea of what style assault rifle suits you best. For eg, I don't like the fire selector, mag release or the whole way mags fit into AR15 variants like M4/M16/SR-25 and I find it much easier to sight down a full length rifle, so a G36c isn't really for me, so I settled on a tactical AK47. I didn't try a bullpup though and still haven't, so I don't know how well they would suit me.
I'm looking forward to giving Airsoft-Ed's L85 a try, but of course, if I really like it, it's tough mammaries for the foreseeable future because I also just bought an L1A1 SLR ...