damn i dont unsterstand this game.
1. What are battle skills ?
2. what those stats, WIl, phy, and so on do ?
We need a guide how to play this game...
As far as I can tell, Str refers to how hard you hit (not sure if it's just physical attacks), Phys I think is physical defense, Willpower is magic defense maybe, and Agi is how likely you are to dodge enemy attacks (and possibly hit your own).
I think "Battle Skills" either refers to just in-battle Str or all stats. There's an ability that increases battle skills by 2 for every turn you're in combat, and it was raising my strength. Don't think it was increasing other stuff but would have to go back and check.
Basically you just do quests or ero missions to get gold and shop XP, use the gold to train stats (either battle or ero), and then once in a while you can level up your shop and spend gold to upgrade various aspects of it.
For a "how to", I'd recommend putting a decent amount of effort in to raising the shop level, because doing so increases the # of Action Points you have (IE lets you do more stuff). Will still need to train & raise stats obviously, but can do that as the battle day draws closer, getting those extra AP is probably priority #1.
Other than that you unlock skills as you increase your stats, and you can pick which skills you want your character to be equipped with. Can check the Arena tab to see info about upcoming enemies so I'd recommend playing around that.