There are two general ways you can defeat this boss.
The first is the obviously hard way, and that's straight up force. Gather enough blue gems from the previous rooms, equip yourself with any staves to boost your attack power, and open up with all of your damage. Then, switch to the Water Crystal (I hope you bought it) and equip any gloves you have. The more, the better! In essence, you want to dodge all of his attacks and hang out in front, then sneak in a charge attack. It may take a while, but you can certainly take him down this way.
The smarter way.
If you perform a combo attack on the boss in his face (3 hit combo, so probably shouldn't use the Wind Crystal), then it will knock him backwards. Take care to avoid his claw swipes while sneaking in another combo, and knock him into those giant fire pits. This will cause him to be blasted out, and land on his back, where you will deal significantly more damage, he cannot attack you, and he will yield more gemstones.
It won't take too many rounds of this to succeed, and you'll win!