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It depends how many images you save.
First, organize your posts by board at the very least. If you like a specific IP enough (video game, anime, etc) then consider starting a folder just for that, especially if you spend a lot of time in threads relating to it.
As a general unwritten rule, for example, you want to be using /a/-related reaction pictures on /a/, /v/-related ones on /v/, /sp/-related ones on /sp/, etc. But you can go an extra mile and be an even better poster by using Sports team specific images in game threads for that team, anime-specific reaction images in threads about that anime, and so on.
For example, pic related is a picture you can use anywhere on /a/, but you probably don't want to be using it on /sp/. And you get style points for using it in a thread about the source material. Anons tend to adhere to this without being told, and it improves the browsing experience because if I like a specific show, I'm more likely to want to see the bulk of the images in a thread at least have some connection to it.