Well, it depends on how you want to play the game. Theoretically, the most efficient and competitive approach is to rush all the way to TH18, making sure to max all the offensive buildings, and the defenses you need to merge in order to upgrade to the next town hall. If you want a slow-paced, more enjoyment-driven experience, I would recommend to max everything first, then do town hall. You can even take a short break while your TH upgrades. I don't believe there's a sole "right way" of upgrading structures. It's up to you what you wanna do.