This is where the error is i beleive
if Selling.Changed then
local Selling = leaderstats.Gold
Button.MouseButton1Click:Connect(function()
Currency.Value = Currency.Value + Selling.Value *10
Selling.Value = 0
`its exchanging gold to money but it think i have 0 gold. Yet i put changed in there to check if the value changed? I dont understand.

3 comments
You need to change gold via server, if you do via local script, it wont be replicated
ok
You can use remote events to solve this because like Leamir said it wont replicate to the server.