If i had an extra $500 on my wallet then i would diversify like this
$150 on Bitcoin
$150 Ethereum
$150 Waves
$50 on ARK
With a portfolio like this you will have a nice profit in a few months, you always must have bitcoin in your balance, you never know when it is gonna make a big pump. Ethereum is more like a long term investment, just like Waves.
Ark will probably rise in the next weeks.