Although the question is simple to hear but answer is not so easy because there are so many coins in the market to treade for short term.But I think bitcoin is unique one among them.
The main thing should be what hes really heading to, which I believe is HODL and it doesnt work that way. As for main trading, he should just visit the exchange of his choice and choose from coins that are listed and trade on them for profit, there are lots of altcoins on every exchanges. Trading is best because youre sure of daily profit if you know what youre doing.