I tried out your server and I thought it was interesting.
-I liked that you could press buttons to play music at the spawn.
-You could see command blocks everywhere.
-You could see a ton of Redstone everywhere.
-The spawnpoint is small and hard to navigate.
-There is no guide or any way to figure out what to do without asking.
-The world is superflat
-You can see many ugly structures in the distance from spawn, you should give us a better view, such as some mountains and a waterfall, or something like that.
-You can jump out of spawn, take damage at spawn, and get hungry at spawn.
-There is a lot of lag and that makes the minigame harder.
-The minigame sign says this:
-A few other signs had spelling errors.
-The messages are activated by command blocks, which is an easy fix with plugins.
-When I entered the mob arena, it was very bland. I would expect more obstacles instead of a tiny square room. It makes it much harder since you can't hide behind things (the archer kit is useless), and when it's over, you respawn with many random items. The mobs also seem to come too fast, there's no break between rounds or place to stop and regen.
-The staff made no move to help me, they didn't even say "hi" or "welcome" when I joined.
-The only way to do something is with commands that aren't listed with /help.
-There isn't any currency
-There is join and leave messages in chat
-The ranking system isn't that clear, and also, just a suggestion, maybe you should add a Builder rank to your server so you have have staff fully dedicated to building new things for your server.
-Is this hosted on your computer? It has 20 slots, so I was just curious. If it is, you should switch over to a hosted one.
This is just my opinion, and I don't run a server, so you don't have to trust me.
-Shadow