This gonna be a single-bot leveling guide from lvl 15 to lvl 61.
Because in my opinion it's pretty slow or almost impossible to let a single bot run through all the high level areas.
lvl 15 ~ 25 Ruins of Agony
At lvl 15 with Top no-grade equipment I love ruins of agony, you can port straight there, and start your bot. And if you die just get new buffs and port (or let port) back there and your bot will be start right away.
Like I said earlier, port to ruins of agony walk a little bit south-west untill you see the Skeleton Trackers (about 1 minute from your spawn point away).
It's a little bit hard until you reach d-grade but works still pretty good.
lvl 25 ~ 35 Windy Hill
This is a great spot, many mobs little spread out so you don't have to fight multiple mobs at the same time. Hunt the giggling wind (lvl 28/29/30) and everything else that is arround. I died a few times untill lvl 30, but after I changed my occupation and had the skills + mastery it was pretty easy. You can also port straight there, start your bot, grab some popcorn and watch your char grown. You just go to the gludin gatekeeper and port to windy will (NOT windmill hill). You should reach lvl 35 pretty fast.
lvl 35 ~ 40 Breka Stronghold
This is a great spot, the only disadvantage is that the Breka Orc Overloards are part of many class change quest, so you might get PK'ed from time to time. But for this level range I never found a better spot until lvl 40. You port from Giran to Breka Stronghold if you reach your spawn point, you head north (slightly north east) up the hill untill you reach a spot with arround 15 mobs. Breka Orc Warrior / Shaman / Overloard.
You get between 1700 and 2100 xp. Drops ain't that bad either.
lvl 40 ~ 46 Hunters Village
In my opinion, this is one of the best spots ever, great exp and good drops. You port to Hunters Village leave the west gate follow the road untill you see a tunnel through a mountain. Just turn left down the hill and start your bot. Tamlin Orc Archer / Tamlin Orc and Karul Bugbears are your target. Non of the mobs are aggressive and there a little bit spread out, which let your bot live for a while.
lvl 46 ~ 52 Ivory Tower
All around the Ivorty Tower, hunt Formers, Former Elders and all kind of Bugbears. Easy and fast kills and mostly nobody is there. Depends if your a fighter or a mage you should walk around the tower until you find a spot that suites you best. All fighter classes won't have much trouble there, for mages you should look for a less populated spot. Just port from Oren to Ivory Tower leave the spawn point over the bridge in front or behind you follow them until you reach the forrest and get started.
lvl 52 ~ 55 Aden
Go to Aden and leave the town through the East entrance and follow the way downhill. As soon you reach the end you should already see harta hanishe, Harta Ratman's and Deprives. They might be already green but there still easy & fast kills and good exp. This spot can be taken from other bots just head more north / north-west and wait until you find another good spot. Start your bot and let him do the work. I recommend here because of the close distance to the town, that you set up your pathing to range 1750 / 1750.
lvl 55 ~ 61 Outlaw Forrest
If you can afford it, heave Top B-Grade ready, because from now on, it's getting harder level by level. You start at Oren, from there you port to Outlaw Forrest and head to Border Outpost until you reach the spot with Oel Mahum Warrior & Oel Mahum Witchdocotrs. This is great exp and awesome drops. The money there is pretty good, especial if you have a 3 man bot group. You can stay there until the Witchdoctors turn light Blue.
There not many people around, so you can enjoy watching exp-bar hour by hour.
This is where I leveled most of my chars, you die a few times, but that's the price we have to pay using bots. Sorry that I can't tell right now, what are good botting spots for lvl 61 and above are, because I don't have experience with lvl 62+ areas & L2 walker and I don't want you send to areas where you die all the time and lose more exp then you make.
At the weekend I gonna shot some Screenshots and add this. I hope I could help you guys out. Have fun leveling.