This is a very short article that should help you understand what you need, why and the prices involved. When choosing specific items reference the other article in this section for what are good products or ask in the gun and gear section. This covers the bare minimums so you can really enjoy a day of airsoft.
GUN AND RELATED
AEG (automatic electric gun)
used-$200-400
new-$350-450
NEW INFO-Echo 1 and Jing Gong guns come with battery, high cap mag, charger and gun for under $350!!!
high capacity mag (300-600BBs)
$35-$50
battery
small $15-30
large $20-50
charger
$10-$50 (starter chargers)
decharger (helps keep the life of your battery when storing)
$15-$25
Paintball Goggles
$30-$50
Mesh Goggles
$15-$45
BB's
$25 for 4000
When you do some rough totalling that's around $550 (UPDATED $300-$400) for a used gun with everything you need. When looking at used gun packages that come with batteries, multiple mags, cases, chargers and other accesories consider this basic price to get started and make sure you are not buying something that you do not need like 3 large batteries or upgrades that put your gun outside the club Feet Per Second Limits (FPS). I would never recomend buying your first gun with second hand upgrades, if it can go wrong they usually do. A stock mechbox does fine and can easily be upgraded later.
Gear should also be considered when budgeting airsoft. The Basics for gear are
Good Boots
$35-$55
BDU set (pants, hat and jacket LOCAL PRICES FOR NEW)
$150-180-military issue or close replica
$50-$75 decent chinese knock off
Tactical vest (basic entry)
$50-150
totalling this you get $150-$250.
So to really get started in airsoft it is worth budgeting in around $500-700 to really get started. Now consider that there are some great deals when you buy used gear and guns which can take these prices down a couple hundred bucks.