If you have makeup application skills, you’re more or less set in the costume department. Sure, it helps if you can complement the makeup by sewing or otherwise assembling a full costume, but makeup by itself can get you far. You can see examples of this in Natasha Morley’s portfolio. She’s a film and television makeup artist, and she’s come up with looks including comic book characters such as Spider-Man and Scarlet Witch and characters from film such as Hannibal Lecter. She’s also talented at creating straight up FX and gore effects with makeup. She has several tutorials available on YouTube — like the Spider-Man video linked above. This one isn’t exactly for beginners but Morley breaks down each step thoroughly.
See more of Morley’s makeup creations at Instagram.