Man, the pixel art is amazing. I recognize this is a start and not as complete as you'd hoped, so aside the content/battle variety, I'll just say on the directional input with keyboard - it did seem a little stiff. I recognize it's based on a grid; perhaps banking a keyboard input within a certain window, to execute upon reaching the next block in the existing movement path, could go a ways to make it feel snappier? It's interesting that you can play with a mouse, too, though - I actually haven't seen that before in this style of game.
All in all, very comfy-looking RPG-style game. With your hub area, the artstyle (definitely), functional battle system and the lore, you've got a very interesting project on your hands. I'm curious what you'd do with the battles to encourage more consideration by the player? I was also curious about the crystals - I think your answer there is a good one. Looking forward to seeing what you do. Cool submission!