Question Most 3D Optimized models you've used? Did you notice a difference in changes of triangles and skins

I am trying to figure out the best way to optimize a recently made 3D project I switched to from 2D, and I want to know what tricks you found most helpful when optimizing 3D models making use of skinned mesh renders such as:

- triangle count on model (never above a certain count)
- material count max
- limiting multiple parts of mesh
- limiting number of bones

or if you have only ever noticed differences on say,

- just amount of current objects active or existing in scene (total game objects)
- triangle count didn't matter, unless over a huge number, or under total amount of meshes with a number in view
- material count never really effected it, etc
- etc, etc...

then please tell me about that.