I really have no interest in battling any other time other than this, I don't really like it, I guess.

Meh. But still I'm looking for decent cheap-ish items for battle against Islanders.

Could someone tell me a few good ones to use?

I'm really only wanting to get the Achievements.

I don't know about the harder characters, but Kohia can be beat with an item hunter shield and antihero sword for sure...;D lol