Anyone Know How To Save Leaderstats? (i have api thing on)

Let's start over with the Services. We only need 1 Service: DatastoreService. and RunService, if you want to.

DatastoreServices is a Roblox Built-in service designed to save player data, it is advised to have a basic understanding of Roblox Lua before operating with DatastoreService since it could be confusing at times. There are a few alternatives to DatastoreService, of course, if you want to be more advanced with your data saving; like Datastore2, ProfileService, etc.

Let's get onto the code:

local Players = game:GetService("Players")
local DSS = game:GetService("DataStoreService")
local RunService = game:GetService("RunService")

local Data = DSS:GetDataStore("CurrencyData")

Players.PlayerAdded:Connect(function(plr)

    local Key = plr.UserId.."Data" -- It is recommended to use the plr.UserId

    local leaderstats = Instance.new("Folder")
    leaderstats.Name = "leaderstats"
    leaderstats.Parent = plr

    local Clicks = Instance.new("IntValue")
    Clicks.Name = "Clicks"
    Clicks.Value = 0
    Clicks.Parent = leaderstats

    local Rebirths = Instance.new("IntValue")
    Rebirths.Name = "Rebirths"
    Rebirths.Value = 0
    Rebirths.Parent = leaderstats

    local Coins = Instance.new("IntValue")
    Coins.Name = "Coins"
    Coins.Value = 0
    Coins.Parent = leaderstats

    local Gems = Instance.new("IntValue")
    Gems.Name = "Gems"
    Gems.Value = 0
    Gems.Parent = leaderstats

    task.wait()

    local Loaded, Value, Error = pcall(function() -- // Always use pcall if you're doing an Async
        return Data:GetAsync(Key)
    end)

    if Loaded then
        if Value then
            print("Successfully loaded data")
            Clicks.Value = Value[1]
            Rebirths.Value = Value[2]
            Coins.Value = Value[3]
            Gems.Value = Value[4]
        end
    else
        if Error == nil then
            print("System failed to load data due to an unknown reason")
        else
            print("System failed to load data")
            warn(Error)
        end
    end

end)

Players.PlayerRemoving:Connect(function(plr)

    local Key = plr.UserId.."Data"
    local leaderstats = plr.leaderstats

    local Saved, Error = pcall(function()
        Data:SetAsync(Key, {leaderstats.Clicks.Value, leaderstats.Rebirths.Value, leaderstats.Coins.Value, leaderstats.Gems.Value}) -- // Make sure this is in order and consistent with the Data loading part. (If Clicks is set as Value[1], then set it as the first thing in the table.)
    end)

    if Saved then
        print("Successfully saved data")
    else
        print("System failed to save data")
        warn(Error)
    end

end)

game:BindToClose(function() -- Game is shutting down
    if RunService:IsStudio() then return end

    local p = Players:GetPlayers()
    for _, plr in pairs(p) do
        local key = plr.UserId .. "Data" -- Also, make sure the key are consistent with the other keys.
        local leaderstats = plr.leaderstats

        local Success, Result = pcall(function()
            Data:SetAsync(key, {leaderstats.Clicks.Value, leaderstats.Rebirths.Value, leaderstats.Coins.Value, leaderstats.Gems.Value})
        end)

        if not Success then
            warn(Result)
        end
    end
end)