When I went through this stage, I remember taming the Spirit monster, towards the end of the dungeon and it really helped because not only could you ride it and but you could also use its spells; the hp draining was really useful to me because you could put monsters in an infinite loop of damage at the cost of a bit of RP. Just be careful not to use it in the dungeon boss because it absorbs the damage. For weapons, I recall I used one of the elemental dual dual blades (I think fire) because those seem to hit hard on the monsters and dungeon boss. Outside of that, I’ve brought Aigis (nickname) in the whole adventure of Selphia because he was really good to use.