$4000 is enough for an initial investment to earn $40 a day with trading. I usually earn more than that but I also have an extensive experience in FOREX trading in the last 12 years or so.
You need a margin account with at least 1:100 leverage, alternatively you could trade with a smaller leverage on sites like Poloniex and Bitfinex.

I prefer SimpleFX because I want to use Meta Trader and there just aren't many other exchanges or trading platforms offering altcoins on MT4.

SimpleFX has BTC and a few other coins like ETH LTC DASH ETC and XRP, but their spreads are huge and untreadable short term. Therefore I only trade BTC/USD, AUD/USD, USD/JPY, XAU/USD and XAG/USD (last 2 are gold and silver spot).

My daily target is set at $50 with a maximum loss capped at $100 a day. If I happen to exceed the daily target of $50, profits are locked in via trailing stops and winning trades left to run until either take profit or stop loss are hit. These bonus profits cover losses on bad days.

Initial investment was 200 LTC back when Litecoin was around $25, totalling around $5000. Now the account has 360 LTC plus almost quadrupled value of Litecoin, it is sitting around $28,000 in less than a year.