Based on:

1 : http://tappedout.net/mtg-decks/gishath-into-the-jaws-of-the-beast/
2 : https://tappedout.net/mtg-decks/ixalan-park/
3 : https://tappedout.net/mtg-decks/gishath-and-the-crew-killin-you/
4 : https://www.mtgsalvation.com/forums/the-game/commander-edh/multiplayer-commander-decklists/783415-a-guide-to-gishaths-prehistoric-menagerie

Explosive vegetation - ramp spells:
https://articles.edhrec.com/in-the-margins-explosive-vegetation/

Great primer:


Other suggestions:
https://tappedout.net/mtg-decks/gishy-boi/