More specifically the area near the entrance to Dangruf Wadi. To get there leave from Bastok Market into South Gustaberg and follow the path right. You'll know your there when you come upon a large area of South Gustaberg that has steaming pools of water. Here you fight crabs, bees, and the occasional goblin.
Levels 10-15: South Gustaberg, Palborough Mines, Konschtat Highlands, Valkrum Dunes
At this point you have some choices as to where you can level. If you want to continue soloing you can keep fighting bees, crabs, and goblins in South Gustaberg or you can go to Konschtat Highlands and fight Rock Eaters(which you will find in a little nook on the western half of the map. The second choice is more difficult because the Rock Eaters in Konschtat link. Also, there is a small cave there with a ghost inside(not sure if he’s only there at night or what) and if you get to close it will aggro and kill you. If you can find a party you can head to Palborough mines which can be found at the most northeast point of North Gustaberg. You can get there by either entering North Gustaberg from Port Bastok or entering North Gustaberg from the path closest to the Bastok Market entrance in South Gustaberg. There is an upper and lower North Gustaberg and if you take the path into it that is nearest to the Dangruf Wadi entrance you will find yourself on the lower half which is where you don't want to be. Make sure before you enter Palborough mines that you buy a map or else you might find yourself hopelessly lost. Once in there you should fight Quadavs on the 2nd and 3rd floors(Greater, Onyx, and Veteran Quadavs). If you come across any Copper or Bronze Quadavs just run you don't stand a chance against them yet. While your here fighting Quadavs you should also be able to finish mission 3 since you will see a lot of Fetich pieces drop. At level 12 if you're feeling brave and have a full party you can head to Valkrum Dunes and fight lizards. As you get a little higher in level(13-14) you can start fighting some goblins, but make sure that you check them first.
Levels 15-20: Palborough Mines, Valkrum Dunes
If you're having trouble finding parties at this point you should stay in Palborough mines and solo stuff on the 3rd floor(Greater, Onyx, and Veteran Quadavs). At some point though you need to head to Valkrum and do the sub job quest so it's just more convenient to level in Valkrum. In Valkrum if you're level 15 and have a black mage you can fight Snippers. If you don't have a black mage stick with goblins (Ambusher and Butcher). After you level a few times(17-18) you can fight crabs without a black mage, you can try tier 3 goblins(mugger, leecher, and gambler), or you can fight flies(just make sure someone in your party has poisona). If you have a black mage you should head to the beaches and fight Pugils. One warning though about being near beaches is at dark Bogys spawn at them so its best to leave those spots before 20:00 game time. You can return to them at 4:00.
Levels 20-28: Qufim
At level 20 you should head to Jeuno and do the chocobo quest. Once you've got that done you should head into Qufim. To reach Qufim just keep heading down the stairs you walked down to get to Port Jeuno. Once in Qufim you should fight worms first, then crabs, and last Pugils. Worms aggro but if you have a good party they are easy to kill. Pugils also tend to aggro so you need to be careful when luring them. Try to get to a safe place in this region before it gets dark. If you don't you will run into Wights and possibly Banshees which aggro from very far distances. Wights you should be able to kill pretty easily by level 24 but banshees you should run from all the time. Other things you need to watch out for in this area are dancing weapons and elementals(thunder especially).
Level 28-30: Battalia
You can actually start fighting earlier then level 28(26 being the earliest I think) but 28 is the level when Qufim starts to really be a bad place to level. You can find this zone just by exiting Upper Jeuno. This is a good place to level because there are numerous safe spots you can pull things to throughout the zone. What you want to do is head into one of entrances to the Eldieme Necropolis. They are the stone entrances into hills that you see all over the place. Most people pick the one that is nearest to Upper Jeuno entrance. From here you can pull crabs and goblins. If you happen to get into some trouble you can zone into Eldieme but I would strongly suggest that you don't walk in any further then the entrance. The undead in there are very nasty.
Level 30-33: Davoi
Davoi is the orchish stronghold. From Battalia head into Jugner until you cross a river. As soon as you cross the river turn south and you should find the entrance. Here you fight Orchish brawlers, beastriders, impalers, and one more I can't remember at the moment:).
Level 33-45: Crawlers Nest
