For me particularlly my favorite training area(s) are the pharos ( not the maze area, but rather in the lower levels) the maze area with the chicken things and horse watchamacallits are ok until you reach like....40's or so. once there then the lower areas r much better fr training. what i did wen i first began training was i completely OD'd on my party with powerups. giving haste, protect, shell, bubble, to all, and bezerk and bravery to one or two of em. along with the embroidded tippet it becomes a pertty good training ground
PS: if you've been able to defeat the mark in the bottom of the pharos with no problem, then the monsters there shouldn't b very hard.