I have a stamina Billboard gui that I want only the person with the GUI to be able to see, so that others can't see their stamina GUI.
The easiest way to do this is to set the BillboardGUI's parent to StarterGUI.
After you have done that, create a LocalScript and when it calls for the Billboard Gui, add this in:
local bgui = game.Players.LocalPlayer.PlayerGui.BillboardGui --Change "BillboardGui" to the name of your BillboardGui bgui.Adornee = game.Workspace.Part --Change the path to your object.
If you need anymore help, I'll be glad to assist. :)