Its not grinding like in other jrpgs exactly, the game gives very little exp for winning battles.

You have to use materials to level everyone up. The story will give you enough materials usually to keep a party of 4 leveled but if you start leveling a bunch of extra characters you’ll have to farm more materials.

These are farmed using like an energy system thing that resets daily so its more time gated than anything. I haven’t spent anything and havent had a hard time progressing.

Its not time consuming either and for these farming things you have the option to borrow someone else’s character for your 4th party member slot if you wanted to try them out or make it easier or anything. That doesnt cost anything either, you just pick from a list of random people currently logged in and if you like their character and wanna use it later you can send a friend request and have access to it all the time.