How do I only make a gamepass work once?

To do what you're trying to accomplish, we need to set up a DataStore, which we will fill with the users that have bought the GamePass.

First, lets define the DataStore key that we'll be using, and the gamepass required.

local ds = game:GetService("DataStoreService"):GetDataStore("IncreasedGold")
local passId = 198893078

Now, lets have whenever a player joins.. we check if they have the gamepass. And if they have the gamepass, we check if they have data stored already. If they have data stored already it would mean that they've already been awarded the gold because if they don't have data, but have the gamepass.. then we're going to set up data(:

game.Players.PlayerAdded:connect(function(plr)
    wait(1) --Just to be safe
    local key = tostring(plr.userId).."_Bought"
    local data = ds:GetAsync(key)
    local stats = plr.leaderstats.Gold
    if data == nil then
        if game:GetService("GamePassService"):PlayerHasPass(plr,passId) then
            ds:SetAsync(key,true) --The actual value doesn't matter
            stats.Value = stats.Value + 50000
        end
    end
end)

So, lets put this whole script together. It should look like this:

local ds = game:GetService("DataStoreService"):GetDataStore("IncreasedGold")
local passId = 198893078

game.Players.PlayerAdded:connect(function(plr)
    wait(1) --Just to be safe
    local key = tostring(plr.userId).."_Bought"
    local data = ds:GetAsync(key)
    local stats = plr.leaderstats.Gold
    if data == nil then
        if game:GetService("GamePassService"):PlayerHasPass(plr,passId) then
            ds:SetAsync(key,true) --The actual value doesn't matter
            stats.Value = stats.Value + 50000
        end
    end
end)

I also suggest maybe adding a checking with a CharacterAdded Event, so that the player doesn't have to rejoin upon buyig the gamepass.

If you have any other questions feel free to comment on my answer or PM me on the site(:

Well what you need to use it a Developer Product. You can use this script and just add the amount of cash you want it to add and also the ID of the Developer product. Dont forget you have to put this script in StarterPack.

local MarketplaceService = Game:GetService("MarketplaceService")
local ds = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")

CASHID = 19382769 -- Put the Developer Product ID here

MarketplaceService.ProcessReceipt = function(receiptInfo)
    local playerProductKey = "player_" .. receiptInfo.PlayerId .. "_product_" .. receiptInfo.ProductId
    local numberBought = ds:IncrementAsync(playerProductKey, 1)
    for i,v in pairs (game.Players:GetChildren()) do
        if v.userId == receiptInfo.PlayerId then
            if receiptInfo.ProductId == CASHID then


                lds = v:FindFirstChild("leaderstats")
                if lds ~= nil then
                    cs = lds:FindFirstChild("Money") --Change to your leaderstat
                    if cs ~= nil then
                        cs.Value = cs.Value + 10 --Change to the amount you want this to add
                    end
                end
            end
        end
    end
    return Enum.ProductPurchaseDecision.PurchaseGranted     
end

Also here is the script to put in the GUI so that they can buy it:

local MarketplaceService = Game:GetService("MarketplaceService")
local productId = 22137544 -- Dev Product ID

script.Parent.MouseButton1Click:connect(function()
    MarketplaceService:PromptProductPurchase(script.Parent.Parent.Parent.Parent, productId)
end)

Make sure that is a local script in the GUI. You can create a Dev Product by going to your game and hitting Configure this place then going to developer products and creating one. If this help please thumbs it up or accept answer!