>>38567247No stamina.
You can re-enter the last 3 areas you visited, even lock one so it never leaves rotation. Feathers that are used to "scout" new areas drop often.
The gems are used for speeding up the ore opening process which is how you obtain items that boost cp levels.
Each boss requires a specific cp level mon to advance which is where the grinding and waiting comes in. I've already hit the point I need to upgrade gears (loot from ores) to even advance, and it takes hours for the bigger ores to open.