This is a small amount for investment, so I would advise you to invest them in a coins those last year had a fairly high price, but now relatively cheap, they have the potential and you can buy more.
$500 is really small amount. He can collect XRP (Ripple) & Waves for long term holding.
It will be good investment. If he had more than $1000, then I would like to suggest for Litecoin. Litecoin is good for future.