This game is not hard, you just don't know how to junction. Summons are utterly useless except for two or three late game summons. This game will be too easy once you learn to junction magic to your stats. You will overpower everything at that point.

Also, one thing you should know is to teach the bonuses like str + 20% 40% etc. to your GFs first because some of them will eventually let you learn an ability that will give you +1 to strength (or magic, or spr, vit) every time you level up.