>>279115653
most common around here is "frankenstein" where you take an existing model you want (ripped from a game or whatever) and customize it over time in blender etc.

Making a model from scratch essentially involves all the same workflows, but if you already wanted to be master chief or a vocaloid why not work with something that exists? There's also heaps of free clothing and accessory models on bowlroll/booth/deviantart, again less reason to reinvent the wheel.

If you have an (anime) avatar idea that doesn't exist, there's plenty of detailed character-creation tools out there that are explicitly for vr avatars (vroid) or can be repurposed for that task (custom maid 3d, koikatsu)