I'm torn and i don't know what to get! The Dungeon looks like the coolest expansion but I've heard highlands is better for getting more gold circulating in the game and I want my players to be able to take full advantage of the commerce options the city offers. I've also heard sacred pool is good for expanding the basic adventure card deck a lot. Any advice welcome!

Cataclysm is the best.

Since the game is going OOP (out of print) , if you like Talisman at all, get all the expansions while you can. If you insist on getting a select few, there are dozens of threads here and at BGG where many of us have given our opinions on which expansions to get.

BTW, why is this question being asked in the Homebrew section?

Yeah the expansions are all selling up fast so I would get whatever u can before they sell out. Frost March, Pools and Blood Moon will increase the adventure deck the most. Woodland most interesting out of corner expansions you don't have though you'll prob get most use out of Highlands.