What if I deposited 20$ .. Can I make them 100$ in less time?
Without a base money, you can make way more than $100 in less than 3 months by doing any of the following.
1. Participating in a signature campaign. I'd say this is the surest way of earning bitcoins without a base money but you need to make a certain number of constructive posts in a week and you get paid on a weekly basis.
2. Doing online jobs. You get paid in bitcoins by offering your services online. These services maybe website designing, graphics designing , writing and so on
Having $20 as base money will make youget more than $100 in three months by just holding it. You constantly and diligently follow the btc/usd exchange chart and then you know when to cash out.