MrPopo: It's also utterly unnecessary to get up to +63 bonuses to beat the game. I finished with one +20 item and then a bunch around +8-9. You're going to get enough gear drops that if you can't use a particular one you should be fine to just wait for another one you can use.
Also, actually getting a +63 bonus (which, again, can trigger a bug that makes the item count as cursed, so not recommended) with Enchant Item requires 3100 SP for the last cast. With 50-59 INT (highest you can reach easily), you get 11 SP per level, which gives you only 2805 SP at max level. (You would need to be level 282 to get that much SP, and the level cap is 255.) With 100 INT (most easily reached at a certain date range late in the year), you get 14/level, which allows you to reach that point at level 222. With 255 INT (reachable with stat trades in the dungeon or via what could be considered a glitch), you still need to be level 141. Reaching those levels will take a while, and I am pretty sure your levels don't need to be *nearly* that high to complete the game, not to mention that high levels cause other issues (like Protection from Elements/Magic overflowing).
I could add that you will need to rest to restore your SP after each cast when enchanting items to high bonuses. You can't just use fountains, as they only set your SP to 200, which is only enough to get the item to +5.
(Of course, this is ignoring the fact that each cast costs 50 gems, but that's paltry in comparison.)