What set of textures for different different resolutions?

Question

Android

I'm making a small mobile arcade game for kids. Everything is ok, but I see that it looks different in different phones: somewhere it’s good, somewhere it’s small.
It is clear that we need textures of different sizes for different screens. I have a plan: I will make two sets of textures: small 50x50 (for a screen with a width < 1000) and large 100x100 (for a screen with a width greater than 1000).
The plan seems to be not bad, but what if someone has real experience - how many texture sets do you use, what are the guidelines for screen sizes?