On top, there should be a list of the things you can buy, like items, materials, familiars, dragons, etc. I would recommend changing the search parameters on the genes depending on what you're looking for, there's a real cool guide to their rarity here:
https://www.google.com/amp/s/aminoapps.com/c/flight-rising/amp/blog/when-scrying-isnt-enough-a-genetics-guide/o3M5_me2hduDmJRjPPo5vagqaRLYDBwvxeD