Random gear on touch isnt working ???

The problem here is that you only have the index for the random gear, not the gear itself. :GetChildren function gives you a table of children of an object. Here is your script's fixed version:

local Gears = game.ServerStorage.Gears:GetChildren()

script.Parent.Touched:Connect(function(Hit)
    if Hit.Parent:FindFirstChild("Humanoid") then
        local Player = game.Players:GetPlayerFromCharacter(Hit.Parent)
        local Inventory = Player.Backpack
        local RandomGearIndex = math.random(1, #Gears) -- PROBLEM HERE
	local RandomGear = Gears[RandomGearIndex]
        RandomGear.Parent = Inventory
    end
end)

You might also want to add a debounce to your script if you don't want the player to get a lot of gears at once but I won't include that here.