1. Best indoor may be The Hole. Just doing the zone's first 8 to 12 mobs(all the way to ramp to castle will yield great experience. At 54, I was there and got really good experience even with about a third being green. You need a good group and someone to mez and one to snare so you kill singles.
2. I think Bugs and Bats in Sol B were the best experience if you don't mind running to the zone on a regular basis.
3. Indoor can try Lower Guk but waits for groups can be outrageous.
4. By 47 or 48 you should be trying your luck in Karnors. Great thing about Karnors you can lfg in both Karnor and Dreadlands. But in all truth Karnors must have a zero experience bonus cause the place sucks for experience.
5. Velios? by the time I got to Velios it was mostly green in the doable zone. I don't have asuggestion here.
Outdoors:
1. Also try outdoors the Burning Woods. You can get ok experience until level 56 at least. Go camp at giant fort with a group and pull everything in sight. You will have lots of variety there.
2. Dreadlands is a place with lots of to kill from level 35 up to about 50. Then things start getting a bit lean.
3. Solo wise I did worms in FV to get thru level 45. With good weapons and armor you're ok but at 46 the experience solo is essentially gone. Go to the dirt area and put your back to the cliff wall and pull worms there with an arrow. The pathing when they run will take them along the wall a ways. Hopefully you are lucky and have jboots. Keep sow up at all times just in case.