The main rule of any amateur investor is to invest such sum you won't regret to lose. I'd recommend to invest about $300 and try to trade and make it be $500, then $700 and finally $1000. Then cash out that $300 you invested and move on with $700.
For that much low investment suggest him to invest in currencies which has low price so he will get a chance to earn high profit.
My suggestions for you are DOGE, DIGIBYTE, REDCOIN, SIACOIN, LEVIARCOIN,DOVU, NITRO etc.