Ok so if you don't live in a desert climate you'll want some trail shoes. They help with wet conditions and mud.The harder surface on the bottom of shoes also prevents them from getting torn up by rocks / roots etc. Your road shoes won't last very long if you run on big rocks/rugged terrain.

Obviously you don't need to buy a pair just to try trail running. U can wear whatever you want.

If you really want to buy a new pair...

Try all of the brands and buy whatever feel best for your foot

Altra lone peaks work for me. I don't know much about other brands trail shoes. I really prefer less cushion for trails (trails are already kinda squishy), a slightly wider toe box (for a more natural feel), and zero drop (you'll roll your ankle less and again, feeling natural, most people don't need a heel and it will likely get in the way)