[Hectic]

m4 416 ak47/74/akm scar l all of those are popular easy to use and have alot of upgrades and acesories available.
Echo1 JG even cyma are cheaper entry lvl decent manufaturers
VFC ClassicArmy KA are more expensive higher quality stuff
depending on your budget
Id suggest finding a game in your area and then asking in the game thread if someone can rent/loan you a gun then while you are there yiu can check out different guns and see what you like and what feels good in your hands and make a beter choice, nothin like buyin an M4 only to find out you like an AK way beter
again if your not 18 id just wait till you are and in the mean time you can search google and these boards and find answers to all your questions