If you don't have patience you will never get far with uploading your own model.
For those looking to upload their own avatars:
You need
Unity Personal,
Blender with
mmd_tools+
Cats plugin for mmd files and the
VRChat SDK for Unity. (Optional but recommended:
CubedParadox's Shaders for Unity, be sure to watch the video in the Cats link so you know how to use it as it's pretty crucial). If you want to use models from the Garry's Mod workshop you will have to download it first, use a .gma extractor like
Gmad and use
Blender Source Tools. You want to export to .fbx whenever you're preparing it for Unity, if for whatever reason your model does not have rigging you can use
Mixamo and upload your model and download the T-Pose animation. Read the pages that I linked and you will find out how to install them. I'm still relatively new to all of this but it's fun to learn everything and just seeing the model work you got from some random nip website. Just a reminder though, you can only upload models up to 20,000 Polygons which means you will have to use the decimator tool from the Cats plugin or re-mesh it entirely, though I am not sure how that works so I will find out later.
Use these websites for .mmd models (translate the pages)
DeviantArt MMD-Mall
Nicovideo
BowlRoll
Tutorials I used:
Once you have enough experience you can try to make some custom animations and maybe get some shitshows like these to work:
https://gfycat.com/BigGlitteringFlicker
https://gfycat.com/IcyNeedyBilby