First thing to do is actually play HoT , it will help you by thinking of how you make builds. Builds that did work in core game may not work in HoT. Some enemies are stealthed so be ready to fight them also. Masteries are very important so make sure you learn them. It may help to do some PoF get some mounts first. Do it the way you want, but it is more challenging without mounts. You can work on your elite specialization for HoT it will also help your character