Like most Pokmon cards, the value of Gardevoir-GX depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Hidden Fates Shiny Vault)
Smooth fixing with Command Tower, Path of Ancestry, Exotic Orchard, Unclaimed Territory, Secluded Courtyard, fetches like Evolving Wilds/Terramorphic Expanse, and tri-lands (Seaside Citadel, Sandsteppe Citadel, Arcane Sanctum, Frontier Bivouac, Opulent Palace, Crumbling Necropolis, Savage Lands, Jungle Shrine, Mystic Monastery, Nomad Outpost)
Tribal/typal decks are ones in which your creature type really matters as the core mechanical aspect of the deck
Most Boros keywords are focused around combat, like Double Strike, First Strike, Battle Cry, and Mentor
Grade: 1.5 You Come to a River There are better ways to win the tempo war, but Find a Crossing has the potential to steal games, and Fight the Current can help you slow down many threats (or recast your own)
Graded Population Report: Ninetales [Reverse Holo] #20 Visualize the distrbution of grades in the chart