Token Gold can be used to purchase any packs in game.
Buying Token Gold in the game or via a top-up platform doesn't count as making your first purchase, nor does it count toward your total top-up or any other top-up milestone. However, spending Token Gold on in-game Bundles during the event does count toward the progress of any top-up milestone event.
You can buy Token Gold regardless of your level, but you must clear Main Story Stage 1-3 before you can access the in-game Bundle Shop and use your Token Gold there.