Of course you can do this. You just have to buy btc or ether with your small amount and start trading with them in an exchange. But bear in mind that some coins can`t be bought under 10$
everyone can start trading with any amount but if you start with a small Sure you will lose because the trading need a big money more than 1000 $ to profit a respectable amount evry month .
Starting trading with the small amount of money in case you have some money in your account other than that of investment amount is really a good idea.
This will help you in understanding the things in a better way. Moreover, in case you suffer loss, then youll lose only a portion of your money. In case you have only few amount and with that amount you are planning for trading, it is really a very risky thing.