If all you have is $100, you're clearly not ready for airsoft. To be competitive and self-sufficient, you need to spend at least $400-500, probably more. At the absolute bare minimum, you need:

Goggles - $40 and up
Gun - $200 minimum for a used pistol, $350 minimum for a used AEG
Battery and/or Propane Adaptor - $40-$60 each
Battery Charger - $70 and up
BB's - $25

That just gets you into the game, and you're going to get "pwned", as the kids nowadays say it, buy those of us who have multiple highly-upgraded guns worth $2000+.....

My personal collection is 6 AEG's....total value about $4500. I've got about $2500 in other assorted gear (BDU's, mags, batteries, radios, backpacks, boots, vests and load bearing gear, etc.)

This may sound odd, but how old are you, and what do you do for a living?