Ok there is no easy way to beat bosses but the most effective way for me for bosses is to take a snap of them then find out what element they are. The use a hard hit move or hard hit steller to take down his stoke gauge I thinks thats what it's call.(its the thing that lets you preform double/combo attacks) so then he wont waste one of your guys in one move. Then once his stock is down use a high angle or low angle attack depending on wether he is flying or not. Try to use combos on the boss because then you could knock him in the or ground then when he it in the air or on the ground(remember your using a double to do this or combo) you use and a steller like gale rod or another steller that knocks them to the ground or sends them flying or you could even use a hard hitting one but if you can try to make it the oppsosite of the monster you are battling(water beats fire fire beats water. its kind of weird but try and look in the manual that came with it it will tell you) it's up to you. But wen you knock a flying to the ground it's basically the same thing.
P.S. Do not knock a flying in the air or a ground to the ground because well theres kind of no point. Know a flting in the air you can't get it with a knock down attack. Knock a ground to the ground is kind of pointless but it still works but then you can't use midrange attacks on it.
Now this part is just a problem where you face the Ronwei. The terms is that you can't use special skills (such as Druken Fist, Sereneta, Thorn Whip and Calorie Drain) and you must beat the monster with a combo of 30 hits but here is an easy way to do it. First you should increase the number of hit places on your Judgement ring. Then you try to give your character the Gale Rod Stellar. Once you're in battle try to keep doing double combos by knocking the Ronwei into the air and use Gale Rod. NOTE: If you're willing to use Shania make sure she attacks at the end of the combo becuse you can use Combo Magic by keeping up with the combo. The attacks are EXTREMLY powerful but keep in mind that if you haven't got 30 hits and you're going to use Combo Magic then choose your attack wisely because some only use one or two hits to make a powerful finishing move. CAUTION: I'm not quite sure if it was Gale Rod that I used to defeat the Ronwei.