If I'm looking to grind medals, I like the Elite Scavenger hunt, Elite ore hunt, and Elite Hide and Seek
If I'm playing for fun the elite market price bug catching tour
As for secondaries, the Elite Hide and Seek, the Firefly one and any hard diving tour! Love these challenges!
For least favorite, the Labyrinths. i just suck at these so badly, lmao not quite found of these, so i don't even try anymore. There are other tours, so,,,
Shark-Battle Tour - I masterfully caught each shark and got 15 medals for it. Hammer Tour - It's so much more fun with three friends. The moment my friends and I flipped it over, I started laughing my ass off because we were smashing the heck out of it! x'D Hide-and-Seek - I remember I was playing with a friend, and she found a villager hiding behind a Sphinx. It was funny because the villager was sticking out like a sore thumb. xD Scavenger Hunt - I like finding things and putting them in the same house.
It's a tie between Elite Scavenger and Elite Ore Hunting. Both are very easy and give 16 and 15 medals respectively. Although if I'm doing tours with someone else, I prefer catch and release tours. That way, you earn whatever medals you get plus extra medals depending on how hard you worked. Win-win.