Within the hints and tips it says that you can't cheat the system, this is not true.
When you enchant something it autosaves to the slot that you last saved, so after every successful enchant you should save to the other slot and every time the enchant fails you should return to the main menu and and load up the oldest save game, the newest one will be the one with the failed enchant.
Also, combos are not everything. When you fight you get rated with either D, C, B, A or S. The rating depends on hoe many things you got in the optimum range. These things are time, combos total, max combo, damage taken, potions used, skill damage, dash damage, charge attack damage. If 6 of these are blue, you'll get an S rating. Once you have a few good items and have levelled up a bit you can do the early levels again, kill all the enemies on the first screen with skills, the second screen with dash, and the 3rd with charge. If you don't do any normal damage then those 3 should be blue, do it quickly for the time to be blue and don't get hit much to get damage taken and potions used in the blue.