If you have Noctis, I would suggest him first. Largely because Cecil and Yoshi have competition for their spots with WoL and Tilith breathing down their neck soon. Noctis takes Cecil's LB and slaps it on a high damage move for a character whose spot is largely ensured for a long time.
30 fucking crystals to activate.
Noctis LB is really cool but i dont see it viable in a "real" battle really.
Or the battle ends first or when you can activate it you are already fucked.
Olive's TM is better to farm then because is so easy to spam