>>385299485
Before you finish in your 3d modeling program of choice, make sure that:

1. Your model is properly rigged and weighted with a humanoid armature
2. You have shapekeys created for speaking visemes (Refer to https://docs.vrchat.com/docs/creating-your-first-avatar#blendshape-visemes and https://developer.oculus.com/documentation/unity/audio-ovrlipsync-viseme-reference)

After you're all done with your model, export it as a fbx. Go install unity and the vrc avatars sdk. https://docs.vrchat.com/docs/current-unity-version

Import your fbx to the project and follow the steps in https://docs.vrchat.com/docs/creating-your-first-avatar#step-2---get-the-model-into-your-project

then you get to spend 20 hours playing around with shaders in an attempt to make it look good