The apes in the jungle are OK for leveling, but are a long ways from anywhere if you aren’t on a server with a map room/teleporter network set up.
Generally, undead give the most experience for the effort. The undead hyenas around the sinkhole and the skeletons just to the east for starters. Then move up to the skeletons outside the Warmaker’s dungeon. Later the Unnamed City, inside Warmaker’s and the wights around the mounds.
Rocknoses give less experience but with a 2hd hammer or mace die very quickly.