World of warcraft human warlock help?

The next place you should go for questing is Westfall, which you can get to by taking the road west from Goldshire. Also you hit level 15, you can queue for random dungeons which can level you up fast, and are a nice break from questing. Once you hit level 20, you can go to Eastvale Logging Camp to get your horse mount. It's located east of Goldshire and north of a the tower right before you get to Redridge Mountains. Just make sure you have about 5 gold or so to pay for both the training and the mount.