For me, the easiest map is creeper for sure. I grind it, and I have 24 completions. It is very very easy. If you use /speed it gets even easier. For medium maps, everyone says sandsoftime, but I think mushroomland is wayyyyyyyyyy easier. I have beat it a whopping 26 times, and it is a very fun map. For hard, lots of people say bluevsorange, but I think spaceship is the easiest. I have beat spaceship 9 times. For expert, lots of people say oceanwaves or shatteredworld. Oceanwaves is horrible. No way is it easy. Shatteredworld is way easier, I have beat it 2 times. Also, I grind slimepk expert, I have 8 completions. These are all my grind maps so this is obviously biased. (By the way, I don't have any recommendations for insane, except maybe ancient :) )