i'm at the part where yuna is sentenced and has to find her friends again, the next boss is that issaru guy with 3 aeons, for the whole game, i've barely used my aeons, and i've level'd up a lot of my characters, but my aeons really haven't had any experience, will i have a hard time wiht the next boss when you can only use aeons? some of my aeons only have like 1500hp .......what should i do to prepare? specifically this next boss

You have a lot of trouble dont you :p

Well save your game first. Then battle around the maze and have every Aeon reach overdrive. You can increase your aeons stats if you defeated Belgamine earlier.

Issaru uses his aeons in this order (ill give tips with it)

Ifrit (Grothia) - summon bahamut. one mega flare attack takes care of him.

Valefor (Pterya) - summon an aeon that can heal itself like ifrit, ixion or shiva. I recommend Ixion since Ixion has a high magic attack and defense. Use Ixions overdrive. The recovery time is high so if Valefor takes some major HP away cast thundara on Ixion. Afterwards change the attacks between Aerospark and regular Attacking

Bahamut (Spathi) - This one is a bit more tricky. I suggest Shiva. Bahamut will begin a countdown before he attacks with mega-flare. Use Shivas overdrive. Hopefully she will recover before the countdown reaches 0. Before it does, use shield to half the damage. Keep attacking and using heavenly strike and healing with Shivas own magic. The battle should be over after 3 overdrives or 2 are used.