I entered Via Infinito around level 50 with all 3 characters. Had them each learn Trigger Happy level 2 and level 3. then made Rikku and Paine each learn Double Exp, Gillionaire and Double Items. Once I got to 40 and got the Cat nip accessory just used it with the Speed Bracer with Yuna in low health to kill everything with trigger happy. Eventually changed Rikku into Dark knight to learn some abilities before getting to Trema. I got to cloister 100 with Yuna at level 77. Rikku at 84. Paine at 91. Only fights I ran from were Chac in cloister 81+.