Before you start the Main Story Questline you'll need to have completed the tutorial, in most games the MSQ is what you do to level up after finishing the tutorial, that's not the case in OrbusVR, it is aimed at those that have already levelled up to an extent or already have one class at max level

I actually made the guide on a spreadsheet so it's fairly simple to follow and see the information you need, you can find it here:

https://docs.google.com/spreadsheets/d/1lpcVgfbrybdk-cNEv4immj4yugPHnOY2A9A89_8bdPA/edit#gid=0