>>292109024
I'd start off with trying to import something from vrcmods first, to get a feel for unity and uploading flow. then try importing an mmd model through blender, then try to add some props or clothesswap to get a feel for the interaction between the two.

If you want to go full custom 3d model though, there are good resources on >>>/3/ just for blender, and modeling in general. There are some classes from cgcookie or blender cloud as well if you prefer that sort of learning. walk you through making a donut or whatever. You can ignore anything about the cycles renderer or eevee though, since you'll be doing the shaders in unity.