What exactly are you trying to do? Can you explain a bit more in-depth?
I'm guessing that these Shinekins(should be Shinekuns) will be stored in a variable that increases every time you win at a colliseum. So then the logic would be:
Enter Colliseum
Do Battle
Get Shinekins
Go to Vendor
Exchange Shinekins for Items
Quit
I'm also assuming that the colosseum will be a map where you can battle enemies. Make it so that once you kill the enemy and you are successful, variable x is increased by a set amount depending on the monster. This can be done with choice commands and simple eventing knowledge. (This shouldn't be copied word for word, it's just explaining the logic behind it.)
Show Message: Who would you like the battle?
Show Choices: Slime, Orc
When [Slime]
Process Battle
Win -> Variable[xxxx] += 5
Loss -> Do whatever you want to
When [Orc]
Process Battle
Win -> Variable[xxxx] += 10
Loss > Do whatever you want to
Branch End
Branch End
You can easily program in the "Shinekins" shop, again with variables and choice commands.
Show Message: What would you like to buy?
Show Choices: Falchion [10], Blazing Sword [25]
When [Falchion [10]]:
Branch - Variable[xxxx] >= 10
Show Message: You got one Falchion!!
Variable[xxxx] -= 10
else
Show Message: You don't have enough Shinekins..
end
When [Blazing Sword]:
Branch - Variable[xxxx] >= 25
Show Message: You got one Blazing Sword!!
Variable[xxxx] -= 25
else
Show Message: You don't have enough Shinekins..
Branch End
Branch End
A bit more eventing to make the system look aesthetically better, some loops to make it more player friendly, and viola; you have what you wanted. I suggest reading up on some eventing tutorials if something like this confuses you. Don't worry, everyone starts out as a beginner!