? | Expected ')' (to close '(' at line x), got 'end'

Al least, I deserve an upvote for this. This is how your code must be looking. Next time, please use Lua block code instead of Inline code.

local Players = game:GetService("Players") 

Players.PlayerAdded:Connect(function(Player) 
	local Leaderstats = Instance.new("Folder") 
	Leaderstats.Name = "leaderstats" 
	Leaderstats.Parent = Player 
	local Stage = Instance.new("IntValue") 
	Stage.Name = "Stage" 
	Stage.Value = 0 

	local function SaveCurrentStage(ply) 
		Stage.Value = StageDataStore:SetAsync(tostring(ply.UserId), ply.leaderstats.Stage.Value) 
		Stage.Value = 0 
		Stage.Parent = Leaderstats 

		Player.CharacterAdded:Connect(function(Characer) 
			local Leaderstats = Player:FindFirstChild("leaderstats") 
			if (Leaderstats and Leaderstats.Stage) then 
				local Stage = workspace:FindFirstChild(tostring(Stage.Value)) 
				if (Stage) then 
					Player.Character:MoveTo(Stage.Position + Vector3.new(0,3,0)) 
				end 
			end 
		end 
end)

Well, there are several issues. I fixed it in next lines.

local Players = game:GetService("Players") 

Players.PlayerAdded:Connect(function(Player) 
	local Leaderstats = Instance.new("Folder") 
	Leaderstats.Name = "leaderstats" 
	Leaderstats.Parent = Player 
	local Stage = Instance.new("IntValue") 
	Stage.Name = "Stage" 
	Stage.Value = 0 

	local function SaveCurrentStage(ply) 
		Stage.Value = StageDataStore:SetAsync(tostring(ply.UserId), ply.leaderstats.Stage.Value) 
		Stage.Value = 0 
		Stage.Parent = Leaderstats
	end -- End for the function

	Player.CharacterAdded:Connect(function(Characer) 
		local Leaderstats = Player:FindFirstChild("leaderstats") 
		if (Leaderstats and Leaderstats.Stage) then 
			local Stage = workspace:FindFirstChild(tostring(Stage.Value)) 
			if (Stage) then 
				Player.Character:MoveTo(Stage.Position + Vector3.new(0,3,0)) 
			end 
		end 
	end)  -- End) for the CharacterAdded function
end)

Lemme now if it helps!