How to save performance with animations?

What if I have 5 or 6 materials on the character and 2-3 on the weapon, but all materials have no texture, because the meshes got colored by faces?
https://www.instagram.com/p/BrkEuGlH9XY

I have no idea how many I can have for true, in the first test with skeletals I had about 150 enemies on screen at 60fps and with static meshes 600 enemies^^
With 1000 enemies I had with skeletals about 12fps and with static meshes about 30fps…
But this was on beginning of development, now I have never tested for a long time.