I don't remember what each of these medals do off the top of my head, but it's definitely a good idea to start using medals that increases your strength and lower enemies' defense. Try to put those either first if they increase for an entire turm or if they increase for a certain amount of attack try to place them near your strongest medals. That's what I do anyway. Like I've got my KH III Sora first in Olympia to boost the rest of my attacks. I do also know that Vanitas is pretty good, so you might want to get him to a 6 star. You also might want to get more medals if you have the jewels to spare because I don't think too many of the ones you have boost strength. Hope that helped any!