I only recently redid my old card collection but Vault X binders are amazing. I bought a few of those (they also have different sizes depending on how many cards you have/want to store per binder). I also bought vault x branded penny sleeves, you wanna make sure you sleeve each card before you slip it into the new binder!

I had the same issue multiples. I ended up storing 2 of the same cards(which are both in their own penny sleeve) into a single slot of my vault x binder. But for many cards, I had 5-10 extras. I sleeved all of those as well and bought Cardboard Storage Boxes and stored them in there!

I also bought some top loaders and a top loader binder for all my holos. I think I only had like 60 or so but this way, the more rare cards are not only more protected in the top loaders, but they can be easily enjoyed if I want to take the binder down and look at them.