Comics where powers get an upgrade either through other characters or artifacts?
I'm assuming apocalypse does something like this? (going off the movie where he evolves/upgrades some mutants)
What you want to search for is “power augmentation”. Theres a bunch of comics that cover it. Search for that term and you'll get a few wikis that have more info and examples.
Are there any characters that have a decent amount of content based on augmenting/enhancing other characters
My money would be with Apocalypse in the Marvel comics. He's got tons of comics about him and his augmenting ability.