5 or 6 at least i guess ..
thottle, pitch, roll, yaw that's 4
1 chan for modes, that's 5
1 for tuning/anything special , that's 6
2 for pitch/roll cam gimbal but not mandatory if you don't need em
+ many more for anything else you could think about
Check out the wiki for the basis , read "the setting up your transmitter" section