Serum is a wavetable's dream come true. Not only does it come with a ton of factory wavetables, but it allows you to import wavetables created by others, as well as make your own. Below are some useful resources to help you find wavetables online, as well as some info about formulas (if you're into that sort of thing).

This goes along with the Serum Lesson Pack for Syntorial, which includes 55 videos covering every inch of this truly unique soft synth. Get the first 4 videos free in the Syntorial Demo.