Ah people always consider Xaldin the hardest member to beat because you can't button mash against him.
Guard is your best friend in this fight, I'd also recommend leveling up your Forms before this fight because they'll come in handy especially already having Aerial Dodge.
Again just guard his normal attacks which will stun him for a couple seconds and gather up as many Learn reaction commands as you can and repeat until you have the max (9).
Continue to just evade his attacks with either guard, quick run or aerial dodge until you take his health down enough for him to start diving at you.
In this phase honestly all you need do is aerial dodge before it hits and collect Learn as many times as possible, which shouldn't be hard. When it's finished you could use reflect to add a little extra damage to him and proceed to use the reaction commands against him while he's stunned.
Afterwards when you trigger his berserk attack just quick run away and wait for him to jump on his Dragon of Lances. Here you can either post up in one corner and cast reflect as it tries to hit you, or Quick Run to the other side of the bridge as fast as you can, which makes not getting hit easier.
When he's back on solid ground just jump over him or reflect when he dashes close to you, and seeing as he's vulnerable afterwards, feel free to unleash an air combo on him. This should trigger him to do his diving attack again and continue the strategy above. Just rinse and repeat and he'll be dead in no time and if you're anything like me (I'm assuming your playing KH2 rather than KH2FM on Proud Mode, you should be able to kill him before he gets a chance to go Berserk).
I don't recommend using Beast Limit considering it doesn't do enough damage for me, but you can if you'd like. If you were going for a Lvl 1 Critical run I'd say use it because you need all the damage you can get on that guy, even though (IMO) he's still one of the easiest bosses in the game.