It is not possible to buy cosmetics, like gadgets or heads or things like that with voting crystal.
Although you can a few exclusive ones for a limited time (atleast you used in past) using it.
Using vote crystal you can now buy things like lootboxes, coin boosters, coins and temporary iron rank.
You can again use the lootboxes to get more cosmetics and use the coins to get talents and washers which in turn gives more cosmetics.
There is no trade of ingame item possible in minigame, along with the features you are suggesting.
So incase you really want them added feel free to make a suggestion
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