Pick a simple goal or idea for your AddOn. It's often a good idea to just make an AddOn that only opens a window or prints a message to get started, especially when everything is new for you. After that works the way it should, and you have learned everything necessary to make an AddOn work at all, you can move on to adding one piece at a time toward your goals. Writting software in general is often a never ending process because you can always think of something new to add or improve.
But now, the Gear Advisor starts popping up, trying to get me to put the old 360 version Ring #1 into Ring #2's slot, since iLvl 360 is better than 350. Except I can't do that, because of the "Unique-equipped" modifier. So I click "Cancel". And then the window continues to pop up after every action my character takes, over and over and over, until I get rid of the old ring by vendoring, scrapping, or destroying it.
Tiragarde Sound and Stormsong Valley are both fairly similar zones, but Stormsong is a little longer, meaning that you might not even have to finish it to hit 120. Tiragarde also comes with a bit of a warning. There are plenty of side quests to do in the zone after you finish the story quests. Don’t do them. It’s not worth the time or the experience you’ll get.
Vol’Dun is the hardest and most tedious of the Horde Zones in Battle for Azeroth. It’s also probably the one that makes the most sense. Each sections of quests leads directly to the one you should do next. For all of these reasons it’s going to be best to get this one done early. Thanks to any legendary items you might have collected in Legion, you’ll be strongest in the leveling process before 115 and weaker after — because that’s when the legendary effects stop working.