I usually say this to people who wanna improve on their OCs, mostly because it works with me.
And I say: try to build on concepts that you’ve already established. Take the ideas that you currently have, and evolve them if you haven’t already
Say, if your OC is an artist, then build on that and turn them into more than an artist, like a sculptor or something like that.
And say, if your OC is a scientist, then try using stereotypes to build on that concept.
And make sure to have it show through the characters. Make sure that their personalities and interests are clear, just through looking at them.
Make sure that their design is consistent and follows one or two connected themes, sort of like a semantic field, but a visual kind.
This isn’t strictly how I do things, but I believe it works.

…not that I’m trying to help you or anything, BAKA

At least you have an oc