luminary gold

Half Desert, Half Forest Map, 3 south of Prontera - A very good spot, as it has PecoPeco Eggs, Pickys, and ChonChons. A much better luminary gold spot is one screen south though....

THE forest, 1 map south and 1 east of Payon - Note the caps on THE. This is the ultimate spot to level, and ALL of my characters spent levels 10-20 here.

Start off with Spores and Condors. When you get stronger, around Level 15, start fighting Wolves.  Around 18 fight PecoPecos. Finally, at 20, fight Wormtails. There is also Snakes, I recommend fighting those at level 25. 

All of these monsters are easy; give good EXP, and great drops. The map is also not very crowded.  A lot of cliffs make for easy sniping too. This is THE ultimate place. I can't stress that enough.

Northeast corner of Prontera - This dungeon is known as Culvert, and I've changed my opinion on it. After you hit about level 20 in THE forest, go here. Go to the 2nd floor, on the 3rd map.

There will be long rows of pipes with no water in them. Most importantly, no aggressive bats, stay here until around Level 27 or 28.