I play with a 360 controller on PC (Mouse and Keyboard felt weirdly sluggish in this game for me...). As a Dragoon, I use about 24 buttons, though only 16 regularly. The abilities that are situational go into the second bar and I simply press R1, use the ability, then R1 to go back to my main bar. This can be done while on the run in a split second. I also changed it in the settings so only these two bars will show up when my weapon is drawn. This way, I don't switch to bars that are useless for combat.