This thread may help understand what James is talking about. Rok engines have better torque than say a Leopard/X30. Not knowing your engine, it may also have an electronic rev limiter that won’t go above say 15,000 rpm. Rotax limits their’s to around 12,500. Peak torque comes in lower around 9,000 rpm versus IAME which peaks around 12,500 rpm and has a max limit of 15,000/16,000.
The point is, depending on your engine characteristics, the track lay out (tight and twisty vs long and flowing) and driving experience, you may have to increase the rear sprocket to get the engine to rev to its potential. That being said, as a new driver, I would recommend gearing targets to just below peak torque range as you exit the corners. That way you get good acceleration until your driving improves and then you can go smaller again as you learn to take the turns faster and roll more speed to the exit. Its a balance and somewhat of a trade off. Better punch at low speed or higher top speed at the end of the straights.
If others at your track are running the same engine, you could ask them for a good starting point and then test up or down from there.