VRC isn't a very well optimized game. However, there are a few setting that can be changed to improve your experience.
The first thing is shield mode.
If you are just hanging out and chatting with people considering changing your shield mode setting from the VRC menu to Max or Custom so player model will revert to a robot default.
Graphic Settings:
Open your VRC menu and select the settings icon.
Click the button to the right of the power button to open the expanded settings.
Click on Graphics on the left hand side.
Reduce your Graphics Quality preset by clicking the - button until you are satisatisfied with the performance.
Some settings can be reduced past the low preset if you need them to be.