The ironic thing is that you'll never know how much you need to mix in until you start flying it in using your left hand.
Then, with the aircraft on the ground, at your feet and tranny in hand, you'll kinda go... OK I tend to use this much aileron (move stick and make mental note of aileron deflection) and this much rudder (move stick and mack mental note of rudder deflection) when I doing an average turn. Then just mix in rudder so it corrisponds.
That's the way. Every aircraft is different so it's pointless giving you some percentages.
Believe me, the best way, the only way really... is to fly in it using your left hand. Flying without using rudder is very silly[]. Once you've discovered it's presence, EVERY aspect of your flying will improve imeasurably. From straight and level flight, to cross wind controll, to all aerobatics... to take off and landing. You name it.
The cool thing is... it's fun to learn.
Enjoy.