$50 and under - nothing good ( boyi dboys, well, and more )
$100-150 - jing gong echo 1 cyma (amazing guns for the price im about to get ajing gong)
$150-200 - classic army sportsline (a lower end version of original classic armysbut still a great gun )
$250-400 - Tokyo marui, classic army, ICS, KWA, and more ( the best high end guns that are actually affordable )
$400 - 800 - TOP, STAR, and more ( giant 20 pound machine guns )
$1000 -2000 - systema ( the ferrari of airsoft guns the best of the best used by police and military to train )
good luck and i would recommend an echo 1 or a jing gong best guns for the money
Nerf gun
The best airsoft gun you could get for $150 would probably be an Aftermath gun, but you could get a JG M4 or M16 for under $150
The one you can afford
If you are just starting airsoft i would highly recommend an aeg, (airsoft electric gun) but if you are pro and experienced, a trained camouflaged sniper is the best, an invisible predator. However it does depend on the user of the gun. If you are asking performance wise then g&g makes the best airsoft guns on the market. (currently in the US)
dont get that gun walmart has the best beginer guns
I say twin ozez are the best cheap airsoft guns
www.shortyusa.com
Definitely Nerf.
it depends on what cheap is to you
The best way - go to near airsoft workshop, give them money and tell what do you want. If you decide to modify airsoft gun by yourself - be warned, this may ruin your gun and even be dangerous to your health.
"Systema" is by far the best airsoft gun brand out there.
An Airsoft gun