SaveData Script (UPDATED)

local DS = game:GetService("DataStoreService"):GetDataStore("Sim_1") -- This is your game key. If you change it, this will initiate a global stat reset. This basically means that everyones stats will be reset.
game.Players.PlayerAdded:Connect(function(plr)
    wait()
    local plrkey = "id_"..plr.userId

    local savevalue = plr.leaderstats:WaitForChild("Points") -- This will be your first value in your leaderstats script, it's cApItAl sEnSiTiVe by the way.
    local savevalue2 = plr.leaderstats:WaitForChild("Rebirths") -- This is your secondary value. If you want to add more, copy and paste the same line and cahnge the number to 3
    -- Extra values will go here. If you have more, it'll be: local savevalue3 = plr.leaderstats:WaitForChild(<Value Name>)

    local GetSaved = DS:GetAsync(plrkey)
    if GetSaved then
        savevalue.Value = GetSaved[1]
        savevalue2.Value = GetSaved[2]
        -- Any extra values that you want to save go here. If you have a 3rd, it'll be: savevalue3.Value = GetSaved[3]
    else
        local NumbersForSaving = {savevalue.Value, savevalue2.Value}
        DS:GetAsync(plrkey, NumbersForSaving)
    end
end)

game.Players.PlayerRemoving:Connect(function(plr)
    DS:SetASync("id_"..plr.userId, {plr.leaderstats.Points.Value, plr.leaderstats.Rebirths.Value})
end)

-- Note: The SaveData script isn't going to work for you on Roblox Studio. In order for it to work, you have to go into the actual game.
-- If the SaveData script doesn't work for you, follow these steps:
-- 1) Go to https://www.roblox.com/create
-- 2) Find your game, click the options button on it and go to "Configure Game"
-- 3) Click the box that says "Enable Roblox to use Studio API Services" to make sure the box is checked
-- 4) Save your changes
-- 5) Shutdown all servers in the game
-- 6) Rejoin the game :D