For now, don't worry about it. Just make sure to use up all your free fights everyday and save up rep points for the perms. Later, when you've hit the level max and are about ready to loop, go make a run for 15 wins.
For the 15 win run, you should have 4 free fights to start off with: 2 as base and 2 from the village upgrade War Room. If you've managed to get the Destiny Warrior or the Matrix of Leadership by luck, even better, but otherwise, you'll need to either farm scratchy for Youma Bloods or save up money to buy tickets/drink doughman daiquiris.
If you really need it, I guess you can spend the arena points you've won on arena coupons, but personally, I'd suggest against it unless you have to: there'll be more shinies in the second season that you'll need those points saved up for.
Well, final thing: You may want to wait on looping until you have all the ingredients for the Letter of Marquis. In fact, I'd recommend that you focus on them first, before you get the duelist items. While together, they do cost a bit more than the duelist's aura, the bonus they give together outclasses it.