The Gastly (76 / 110) card can be found in the Legendary Collection set.
Recently sold 5 times and based on those sales is worth around £49.20.
Currently, there is 1 open listing for this card on ebay.
This card sells in the range of £41.27 to £57.13, making it quite stable.
This Common card was illustrated by Mitsuhiro Arita.