A lot of people will first advise you to get Age Verified. If you are 18+ you can meet up with a local representative who will verify you and you'll be granted access to sections of the forum where you can find retailers and other members selling their airsoft guns.
As for the two you listed, both are alright guns for starters but some people will give the edge to the ICS M16.
You can look for full metal or part metal guns that will give you a bit more durability. FPS doesn't make a huge impact so anywhere around 330-350 fps (with 0.20g bbs) should work.
H&K G36c (KWA) / Glock 18c (TM) / Kimber LAPD SWAT Custom (TM) / Mossberg M500 (ACM)