Step 1: Cheap vs Expensive & Types of Guns
LPEG (Low Power Electric Gun)If you want to do backyard skirmishes and never any real battles, when you would be fine with a LPEG
AEG (Automatic Electric Gun)If you want to do battle, then you will want a more expensive AEG. These AEGs range from $80-2000.
Springer: Most people's first gun.Good for backyard skirmishes, but unless you have a high end spring sniper, avoid these on the battlefield.
GBB (Gas Blow Back) a few rare assault weapons are powered by gas Pistols often are.
GNB:Gas Non Blowback. Generally reserved for cheaper pistols, but expensive ones can be this, also.
Full auto is a clear advantage. Also, don't buy cheap guns for a war. Pictured above, Top: good ECHO 1 G36. Below: Crappy Crosman Mosberg Spring gun