Max level means that it’s recommended to upgrade that particular Battle Art every time you level up!
Each level +20 HP
No HP Constellation, then prioritize this Art
Each level +10 PATK
Each level +7 PDEF
Each level +12 SDEF
Add a little at first and max it later
Each level +12 MATK
Upgrade when you get a Mage partner
Each level +8 MDEF
Not really needed, because of less Mage on early game
Each level +4000 Initiation
Initiation decides whose team strike first
*Note: Ba Gua costs a lot of art points, but its max
level is only 20. It can be upgraded depending on your personal necessity, unlocked at level 55.