Sharpie fine point markers (they don't smear, even on glossy paper):

https://www.amazon.com/gp/product/B019QBOX6U

https://www.amazon.com/gp/product/B00144862U/

Washi tape

https://www.amazon.com/Mr-Pen-Washi-Tape-Set/dp/B08L5PB8N6/

Stickers too, but I have screwed up and gotten ones that are really too big for cards. Now I just pick them up when I see them at the drugstore.