Here's what I do:
Have Quetzacoatl learn Card and the card refining ability. Have Diablos learn the time/space magic refining ability, and Siren learn the Life/Recovery magic refining ability. Refine Diablos's card into 100 Black Holes, and refine those into Demi's for all of your party members. Refine Sacred's (or maybe it was Minotaur's) card into 100 Dino Bones and refine those into quakes. Junction those to your HP and Strength.

Go to Cetra and get Odin, you might want Diablos to learn Enc-None so you have plenty of time to fight him. He won't do anything at all, but you have a time limit, and if it runs out in battle, it's game over. Refine his card into 100...somethings...that refine into Deaths. Junction those wherever you want.

You never really have to draw or level up much, just use lots of refining abilities to get lots of magic to junction.