Don’t be cheap when buying your cleaning supplies. Going to need a good bore cleaner, decent solvent, decent oil(there’s a great thread here about what kind of oil people use). Probably going to need a good bore snake and a cleaning rod set, and a good chamber/receiver brush.
The bore is the only thing you really can’t see unless you have the tools and know what to look for when it comes to cleaning. So they say to run the patch till it comes out clean. I think foam bore cleaner works the best, but that’s only my experince and IMO.