Need a script about a character only having one gear at a time?

Here, What this script will do, what i'm guessing you're asking for is, when a tool is added to player's backpack, any tool/tool he is currently using will be removed.

Place this code inside a localscript inside starterpack.

game.Players.LocalPlayer.Backpack.ChildAdded:connect(function(c)
	for _,v in pairs(game.Players.LocalPlayer.Backpack:GetChildren()) do
		if v~=c and v~=script and v:IsA("Tool") then
			v:Destroy()
		end
	end
	if workspace:FindFirstChild(game.Players.LocalPlayer.Name)~=nil then
		for _,vv in pairs(workspace:FindFirstChild(game.Players.LocalPlayer.Name):GetChildren()) do
			if vv:IsA("Tool") then
				vv:Destroy()
			end
		end
	end
end)

If you need any help please ask.