I've only done runnyeye pre-revamp; I was there with a group at 25 and it was amazing xp but when Borxx spawned we needed a higher level character to kill it for us. It wanders over most of the zone.
I did a lot of sol a and upper guk too. I don't remember if there was an upper guk camp specifically good at 25, but I was there off and on from high teens to 30ish.
I agree with Loramin that kedge is a ton of fun later on. It suffers from its camps having too much variance in the strength of the mobs (e.g. mermaids are level 38 or 39 up to 46), but in large part makes up for that with the zem.
Death deep in paw isn't so bad; I don't remember running into anything that sees invis. The judges camp is some good group xp mid 30s, and was popular pre-kunark.
I second Jibartik's recommendations of gear-motivated hunting and lower guk. You can solo all of that zone's drops while the camps are still blue and some of them are interesting challenges. Even more fun if you can get some friends and go a little earlier. The zone is slow xp due to a low zem, and the gear mostly not so relevant post kunark and velious, but the zone is a real classic.
Tecmos's videos show some 30+ ench solo spots he tried:
https://www.youtube.com/channel/UCkZ...FTW4HZg/videos. From what he covered I especially enjoyed HS North and South, and there's some good if boring xp at that CT crocodile camp.