If I have 0$ at the moment can I make 100$ in 2 or 3 months? How?
What if I deposited 20$ .. Can I make them 100$ in less time?
I'm not so sure if you can, here are some of the first ways to participate in airdrop as much as possible and choose a decent airdrop, second participate in some bounty (signature, social media and artcle / blog / video) but that depends on your skills.
Airdrops can do this but they are very low for trust. Sometimes they won't pay you a single token. If you catch good ones, you can earn this money by not spending your pocket money.