yeah, right now t4 is in beta so there isnt a whole lot of documentation, but there are people here (like me) who know t4 pretty well so we can help. If you have a question just ask it
Right now t4 is just on the 4th beta, which is pretty early and new content is being added all the time, including classes and races.
However, unlike previous versions of tome, t4 makes it so that you have to unlock certain classes/races before you can play them, and mages are a part of this. (if you want you can play a quasi-mage (arcane blade) at the start, but keep in mind they do not regenerate mana like a normal mage.
so have fun playing and try different stuff, and dont be afraid to ask/provide input on what you think of certain things as this game is in a state of flux.
there probably will be a more definite guide a few betas down the road, but right now there still is balancing issues that need to be resolved first.