I have no idea about the freeport side, im sorry, so i will write down places i found out was good solo spots for my warden.
level 10 - Just outside the gates in Antonica or the creatures which cons: Green++ in oakmyst forest. You should be able to kill them and you get around 4% exp per kill.
Level 13 or so - Zombies on the island in the northwest corner of Antonica, i belive it's called the Tomb of Varsoon or something like that. These will be yellow at first but is pretty easy. These works all the way up to level 15 or 16.
level 17 - Darkclaw crabs on the beach at the northeastern part of Antonica. Just watch out for the named crab Stoneclaw which roams the area sometimes.
Level 20 - time to hit Thundering steppes and start doing the small animals here. There is crabs level 20-22 on the beach near the docks, and plenty of snakes, beetles, hawks and antilopes from the docks to the antonica gate roaming around. Be aware of bears tho, as they will attack on sight.
Level 23- Skellies near the ruins of varsoon entrance. There is plenty of these wandering around there, but be careful as these are aggro mobs. Find a safe spot to pull to. These can be done all the way up to 27.
Level 27 or 28 - Orcs in Zek. These will be level 30 solo mobs - so they will con: Yellow to you, but i had no issues with them and the loot here is great. Even the orcish meat is worth 5s each, skulls sell for 35s and weapons and armors and suchs sells for around 1g+ at the merchants.
level 30+ - Keep doing orcs in zek, just move further away from the docks to find harder orcs. The miners can take you all the way up to level 35.
Well.. That's as far as ive reached yet. Hope this helped. I suggest you group alot tho, as it is much more fun :)