As Adek said. CoF/VoH for l1-3 elixes, maybe a few weaps to NPC. SM4 and i guess high GB/low EC respectively.
Mansion and Beast Tower are pointless imho unless *1. Too long, rewards sucks, the works.
GCM is where you can make serious cash on gold alone. Also maxes your elixirs and can make a buck on manuals/books. HM4 iirc.
Beast Palace is my fave dungeon, but why, you have to figure out yourself. Just grind a ck hyb there and you'll know
No idea what level to finish it, what i wanted from there only drops if you can grind it, boss drops are shit and loot is crap.
SrS is a mixed bag. If you go while you can grind there, you'll stack insane amounts of BE, make shitloads of npc weaps per run, etc. If you go when you can actually finish it, mehhhh... Worth doing from the moment you can kill them mobs, which depends on class.
To be truly honest, 9D's dungeons are a good example of godawful design. The level threshold to finish bosses makes most of the dungeon itself redundant, the "killer gets drops" breaks teamwork unless its a group of (good) friends/people, and the time
rofit ratio only gets worse as it goes up. All in all a sad affair.
*1
Don't solo. If you're a healer, find a good ck hyb friend. If ck hyb, find a good healer friend. If none, improvise. But don't solo.
Reason is simple. By design you need to kill a fixed number of mobs in all but a few of them. That means there's a fixed time cost per run. Let's say it's x mobs that take y time to kill. x*y will then be your minimum run time. Let's say kill speed is same for both. Then your run time will be (x*y)/2. If you make two runs, then it's (x*y)/2*2)=x*y, your original run time. Thus, you "waste" same time doing 1 run solo as you would doing 2 runs with a friend.
Now, where's the profit?
Profit #1. 9D has a max mob aggro, so, one char can only "pull" a few mobs. Two chars can pull double that. And AoE's hit anything in the range. If the ck char takes care to only shoot far mobs and aoe close mobs, it's a slaughter fest and cuts time by a very reasonable amount. Thus, you can actually run two dungeons in less time than you could solo a single.
Profit #2. Bag space. In GCM/BP/SRS, loot can be so much you don't have space for everything. Wasted loot = wasted $$$. Choosing loot to take and loot to leave = wasted time = wasted loot. Two chars will have more room to pick "npc junk" without being overwhelmed. And by running as many times as people in party, you end up getting more loot in less time.
Sigh... getting nostalgic... but no good healers these days and solo playing sucks.
