I have no idea what offensive skills you are referring to, but the one offensive skill you should max is the wiggly jelly (landmine).
Does a ton of damage and you can use it in combos.
Don't max the level 60 transformation, you're spending more MP on that then a maxed level 40 transformation, and you're doing about the same amount of damage percentage wise.
Why do you need int potion?
Also, I would definitely consider getting the last 2 summon slime skills (at level 1). Summon slimes has invincibility frames. The freeze slimes are great for...freezing stuff. The giant blue slime is for creating a wall between you and someone attacking you (PvP or stages).
lvl 67 Lime (psuedo-active)
lvl 52 Eir (inactive)
lvl 11 Seig (inactive)
lvl 43 Dainn (RIP)