I see at least 2 options.
1. Buy some WAVES. Tidex exchange is one of the places you can do that. Just pay attention, withdraw from exchange also costs you, make sure you checked how much extra you have to buy.
2. Use faucet. Unfortunately the only faucet I know of is wavesdrop.com and it doesn't pay as good as it used to, so this will take a lot of effort...
I have already tried to faucet on wavedrops.com and it will take me a week before i got the amount needed in order for me to receive the amount i needed.