My daughter really enjoys making cards for her family and friends. My mother got her started with a cute box of supplies - stamps, die cuts, stickers, and ribbon. We also keep a 3 drawer storage container with construction paper, white paper, glue, scissors, blank cards, and things like markers and colored pencils. The drawers make it very easy to pull out what we need for a card or two.
In the past year or so, my mom and my mother-in-law have enjoyed giving her other stickers, shapes cut out of paper, blank cards, and other supplies.
My daughter loves picking out her basic card and drawing tools, then she sorts through her box of decorative stuff in order to find the perfect thing for that card. She made a wild zoo to send to a Grandma for Mother's Day and a frog thinking about a heart for one of her Grandpas on Father's day.
At first she'd mostly use stickers and stamps, but it has also become a fun way for her to practice writing and drawing.