The key to a Gishath deck is in its ability, which states that whenever it deals combat damage to a player, its controller reveals that many cards from the top of their library and may put any number of Dinosaur creatures revealed into play
While Demon of Dark Schemes is a powerful energy card, black doesn't appear in the color identity of most energy commanders, leaving the Demon somewhat stranded for now
It also allows these copies to be sacrificed as creatures for effects that require one, like Trading Posts third activated ability
You can also use your collection (once you have amassed enough of a variety) to build your own decks of 20 cards that you can then use in either solo battles against AI, or against other players online
Bident of Thassa could be an all-star here, combining with all your evasive creatures (especially the likes of Emeria Angel, Faerie Formation, Inspired Sphinx and Skycat Sovereign) and token making spells like Migratory Route and Storm Herd to keep the cards overflowing
Japanese cards also can fetch higher prices, as the Pokemon Company printed them earlier than English-language cards, but are unlikely to prove useful or of interest to many fans