Oh boy I've got some resources for ya!
First, taking pictures of yourself is so so helpful for expression work. I've got an OBS scene that's just a fullscreened camera feed for taking spur of the moment reference videos too, really helps you act through your characters when you can look at someone emoting exactly what you want to get across.
Google maps as jermajay pointed out is a godsend, as is sketchfab for quick 3d references of those tough angles.
https://line-of-action.com/practice-tools/figure-drawing
Line of action is a great resource for figure drawing, in fact I use this pretty constantly to warm up and shake out the tension in my hands. 60 seconds per image for 15-20 minutes. It's like magic.
Nothing can replace a real professional letterer, but these are very very useful lettering guides for getting your text to look more professional!
https://www.reubenlara.com/perspectivegrid/
Perspective grid generators are another essential tool in my toolbag. The top link is free and online, the bottom link is offline and costs a couple bucks, but has some useful features that the top one doesn't.
https://www.photopea.com/
Photopea is a free online clone of photoshop.
https://coolorus.com/
https://paletton.com/#uid=1000u0kllllaFw0g0qFqFg0w0aF
Color wheels are very useful tools for generating colorschemes. Coolorus is conveniently integrated directly into photoshop, but a free alternative is Paletton. Really useful resources if you're colorblind like me!
Anatomy Dolls are very useful in a pinch. I've got a couple different kinds. The Figma figures are pretty flexible, and affordable. The seamless dolls are much higher quality and don't fall apart as you're handling them, but they cost a lot more, and you're sure to get some weird looks if you leave them out of the box hahaha
https://flatto.nl/
An online line art flatting tool. You feed it an image of your line art and it spits out an image that you can use to start coloring.
Notes on self publishing by our very own @joannekwan
https://writersdiet.com/test/
Useful writing fitness test, great for writing punchy copy
As a bonus, here are a few art resources I made myself to help folks out:

If your eyes always look misaligned when you flip, try drawing the horizontal line on your heads straight instead of curved!