Hi there. The 2 most important animations is the idle animation on 4 frames (1-4*) and the running animation on 6 frames. (5-10*)
However; In general, I think it is a good exercise when using premade assets, to leave things up to your creativity. If you can get something out of mixing and matching the sprites, then I highly encourage it.
I hope this helps you along. 🙂
*If the animation system you are using starts on 0 then just subtract 1 from what I wrote.