Use the Grimoire Dungeons to Grind
There’s a lot about Shining Resonance Refrain that sticks to the “classic” style of JRPGs, and that includes the need to grind. At multiple points in the story, you’ll be pretty underleveled compared to enemies in the next area, or an upcoming boss. The easiest way to combat this is by talking to a character named Alfrieda, and using her Grimoire to delve into the game’s dungeons. Alfrieda can be found just to the left of the Seagull Inn, or at any of the campsites around the world. You can choose from a variety of themed dungeons, and items called Sigils can even add various effects on, like making a certain enemy type appear or boosting the item drop rate.
An especially useful Sigil is the Egg Hunt one, which makes valuable egg enemies appear that can grant you massive amounts of gold, experience, materials, or level up your tuning. Taking some time out of your adventure to run through a dungeon or two will do nothing but help, so make sure to do it every now and then.