Chocolates ????? Not sure what you might be able to do with a budget of 1 buck though. If he/she is a friend you know well, you could give 21 handmade cards with something about each year........
by a domain name for them from someone who has too many and doesnt use them u can always get a bargain on here! (might be a crap domain though)
even a good card costs more than a few $, so it is not all that cheap anyway! perhaps some hand made crafts, explaining each year, would be nice, as pointed out above.
exactly chocolate .. what i thought really. as you said "1$ per gift" buy 40 chocolates , different flavor Or pack them with a big box. hmmm dunno whether your 21 age good friend will like it or not...
I say visit the dollar shop clones that exist. everything they have is $1, and they have loads of stuff. A coffee mug?