For a poker card, 3.179mm of bleed to your cards in the dextrous export page. (This number will give you poker sized pngs at exactly 1125 x 825 px).
Export your pngs at exactly 300dpi.
Upload your card pngs to the Game Crafter and follow the prompts to get them printed.
Note: the cards in the video above have already been optimised with bleed in mind, so you'll need to do that first. Checkout the section on Bleed .