Ansem is beatable at level 60 or lower, bt if you'e played the game so many times like I have, he's not a challenge at any level. Nonetheless, you might want to have at least a full stock of Elixirs. Not for this battle, but for the next one. You might have to use at least one, if you hav MP Rage, you probably won't need it.
As far as strategy goes, it's like what Ragnarok said, just listen to him to know the signs for when to move. The obvious one is wen the screen gets darker, he starts glowing and says, "My strength returns." Just Dodge Roll to avoid his Heartless Guardian's popping out of the floor at you.
Just a little tip. When he says, "Take this" and chases you around in his shield, if you time your Guard perfectly, you can stop him in mid move. You'll get some XP Points too.