the grimores help you a lot, especially early in the game. it is a very good investment, cuz you are getting your gil's worth. and try to do chains constantly. there are areas where you can easily get to over a 50 chains (lussu mines, ogir yensa,etc). aside form getting rare items, or loot, you can get 3 times, 4 times as much from one enemy then you would if just kill it cuz in was in your way.
i've got 5 grimores, you get them just by talkin many times to any shop owner, or by looking at the hunt board (i think you get one when you check the board 15 times)
I don't know when I'm gonna finish this game (I'm gonna try a lil' bit more during the holiday) I barely got time to play. tihs week i only played once. I'm in the nam yensa, just about to enter raithwall's tomb, 54 hours, and cht at 25+. you will think i level up lot, but currently I'm not. all I do now it's completely explore an area as soon as it opens up.
I would say you could level up easily just by exploring the whole new area that's given to you, fight every monster you encounter, avoid monster with 10 levels over you, unless you feel lucky and fight them, in that case, perform mist chains, I've been able to defeat 5 dinosaurs in the eastersand, i fought many werewolfs in giza, and level up a lot fighting in the garamisthe waterway (malboros 😖 ). the only things i haven't been able to defeat are the damned elementals.
you won't even feel any lack of license points, and you will through the game almost smoothly.
for those who're just about to play the game, you can make the game much easier for you at the beginning of the game, could be considered cheating, and i think it's recommended to do it on your second run through the game: at the beginning of the game between the eastersand and giza plain, level up Vaan, and Penelo, if you have her, up to level 25, then just continue the game as you normally would, you're bound to keep on leveling, and when you get control of the other characters,they'll be just about the same level as Vaan and with crazy tons of LP.
you'd notice that a monster doesn't give you as much exp points when you're alone, than when you have a party of 4 characters, that's cuz the monster will give the exact amount of exp points, but the game will divide that amount between the numbers of party members currently on screen. that's why what I wrote above will only work early in the game, after that you'll have to level chts individually, and that would take a long time.