Welcome to your new addiction
You will need to for sure stiffen up the suspension to keep the front from diving and bottoming during hard braking. 310mm front is all you need paired with a proper front caliper and matching master. That is just the start of a set up, there are many more areas to change but that is a good start.
I mean like, take my 250xcf for instance, I took a full on trail bike (bought the xcf for the 6th gear) and converted it to a full on SM race bike. Changed suspension, triples, swingarm, front brake and added a slipper clutch and a lot of other goodies but I knew what way I wanted to go on thi build. For you, someone just getting into it, just start with a decent set of wheels, bigger front brake and suspension tweeks. Once there, get out on the track nd put in some laps and a race or two and you will see where you and your bikelack and uild from there. Thats just my advice anyway. I added a before and after to the bike I mentioned.
Good luck with your build and have fun with it.