I honestly find contacts for Homestuck cosplay kind of a waste. Their eyes are all yellow except for the pupil so if you find contacts like that I commend you! But I just find it a waste.
I actually bought my BEN NYE make up from a store called cosplaysupplies.com
Alot easier to use I find.
There is actually a tutorial online of a Gamzee cosplayer doing make up
Its really useful. I hope I helped a bit XD