Do you want to sell your cards and receive gems? I have the right service for you
https://steamcommunity.com/id/scrybotservicebuycard/
You can sell your cards, foil card and booster pack in exchange for gems

Scrybot Service - Is a service which can automatically trades keys for card sets.
https://steamcommunity.com/id/scrybotservice - For people just starting to level up: low prices. Perfect for Steam users with a level below 80.
https://steamcommunity.com/id/scrybotservicejunior - For people just starting to level up: low prices. Perfect for Steam users with a level above 80.
https://steamcommunity.com/id/scrybotservicehigh - A huge variety of sets, which allows you to reach a very high level.