HD Noob Here, Which Expansion to buy first

Hello played the base game in the childhood, without AoC. Now with the Hd version i got Aoc.

I really enjoy playing again, and i wonder which dlc to buy first. I am short on monees, so i can only buy 1 for now. I want to finally be able to host games for expansions and also be able to spectate games. Which Dlc would you suggest is the best for a noob like me?

thank you very much.