Is this the right way?

I've been leveling up my characters and pets evenly as they earn points, but I'm not sure if this is the right approach. Should I be focusing all the points on the top two characters who have the best weapons? Also, by chance, I've leveled up all elements except Earth evenly. I'm wondering if I should level up Earth evenly as well. So far, the leveling up has been going reasonably well. Oh! And about the event tickets, like the four-leaf clovers, cherry blossoms, or rainbow shapes – if I don't use them, will they appear again later?? I'm worried they'll disappear, so I'm using them as soon as they appear.