If you just wanna cover the biggest must sees in Kyoto, then i recommend 2-3 days, or you can concentrate on just spending time in whole Kansai area (Kyoto, Osaka, Nara) and maybe skip Tokyo. Tokyo is big and fun, but depending on what u like to see, then you can also spend a whole week exploring Kansai area. Osaka is full of shopping areas, local interesting food areas (many japanese consider Osaka a bigger food mekka than Tokyo, which maybe has more posh areas), and so on.
But yeah, going to Shibuya, Akihabara, Shinjuku, Shimokitazawa and so on in Tokyo is also pretty cool. But one week will fly by fast.