Really quick note on the best location to level up I've found, which you can use to get all 4 achievements for skills at 35.

Step 1. If you want to get all four achievements for skills at 35, MAKE A SAVE at a different slot you don't touch, to go back afterwards. Max level in this game is LV 35, at which you will NOT have all your skills at 35.

Step 1b <Optional> Wear the magic ring.
Step 1c <Optional> Stock up on magical herbs. You can buy 99, and at this point, money shouldn't be a problem for you.

Step 2. Go to this spot on the Astral Plane



Step 3. Go through the warp and warp back. Move one square up and cast Shadow 2. All four enemies will die, giving you 2,000 Exp. (don't mind the stone gargoyle, that only gives 1 exp)



Step 3b <Optional> There's a shadow guy at the left. If you are limited on items and have some extra time, you can try to get him as well for an extra 500 exp, total 2,500 exp. Sometimes, he'll even randomly join the party, which is nice!

Step 4: Go through the warp again, repeat.

Step 4b: <Optional> Use magic recovery items, like potions or herbs

Notes:

- In later levels, if you increase your magic skills, you can easily level up each time in less than a minute if you use items
- Your bottleneck is the amount of magic you have. The magic ring helps,and if you've saved magic potions or buy herbs, this will also be faster
- After level 25, each level only requires 20,000 exp!!
- I've done some math and looking at different spawn point and I believe this is optimal, unless I've missed a spot somewhere. There's another spot on the east in the same floor that also gives 2,000 exp, but it takes slightly more time. There's also a few spots on the last floor that you can just walk around and find enemies, though it's slightly slower, can help you get the dragon achievement.

Let me know if I can improve this guide in some way!