My favorite to go courses, free and paid, are those by:
Matt Kohr
Modern Day James
Marco Bucci
All three are very charming and very good teachers who create short form videos on youtube or their website. The majority of there videos are short and to the point, but still very full in depth and understanding. I've purchased a lot of their paid content and they're even more helpful as they go more into detail of what they show with their free content.
Another artist I love is Stan Prokopenko on youtube. He's just as charming as the other three but I just separated him from that bunch because I haven't had the chance to purchase his paid material yet. But his free material and podcasts are abundant on youtube and are extremely helpful!
Proko
Other courses that I haven't tried yet but heard about
https://www.nma.art/learn/
https://artcamp.com
Reference Packs
https://gumroad.com Gumroad has a bunch of reference materials, free and paid, so I recommend searching the site
Some good books:
Color Theory for the Makeup Artist: Understanding Color and Light for Beauty and Special Effects by Katie Middleton
The Complete Guide to Perspective Drawing: From One-Point to Six-Point by Craig Attebery
Framed Ink by Marcos Mateu-Mestre
Framed Perspective Vol.1 and 2 by Marcos Mateu-Mestre
Perspective Drawing by Sarah Haley
Comics and Sequential Art by Will Eisner
This list has gotten pretty long so I'm going to stop here.
I hope you find something helpful from this!