There is a whole theory of localisation within the context of ring theory that uses Gabriel's notion of quotient category. A starting point might be Popescu's book: Abelian categories with applications to rings and modules, if you can get hold of a copy. The theory has an immense literature so I will not attempt to give a list (do a Maths Review search with a long search time frame!!!!) A related area is that of Torsion Theory, so search on that as well.

You do not make precise what areas of application might be of interest to you? Perhaps looking at the book by Gabriel and Zisman would indicate another (non-Abelian) perspective. That leads on to localisations in Quillen model category theory and beyond to triangulated categories, and ....

Serre's classes also have applications in profinite group theory (pro-$\mathcal{C}$-groups), but that uses the localisation less directly.