That's what I had figured on your budget.
16 (14+2 backups) spyders at around 20/each would be 320 bucks.
You'll be able to find some a little cheaper in bulk, and some a little more expensive. Sometimes the packages that show up on ebay will include tanks and hoppers. Estimate that at about 50% of the guns you buy, and add 10 bucks/ each unit that needs one.
That's 8*10. 80 bucks.
What do you plan on doing for air and masks? And paint. Remember that one huge advantage a field has is all-day air. And that could be a damning investment for you.