The Garchomp V (TG23) card can be found in the Astral Radiance Trainer Gallery set.
Recently sold 15 times and based on those sales is worth around £21.00.
Currently, there are 13 open listings for this card on ebay.
This card sells in the range of £15.05 to £26.95, making it quite stable.
This is a Trainer Gallery Rare Holo V card.
The fact that it is a V card makes it one of the more valuable cards.