What You'll Need
Because I have a whole arsenal of artist-quality materials, I tend to use them for our crafts together and I'll list them below. That said, it's completely unnecessary, and I'll include a more cost-effective option, too. I included links to Amazon for convenience!
We used white cotton Stonehenge paper, which takes paint beautifully, but any kind of heavier paper like Canson Mixed Media or Canson Acrylic Paper would work. Of course, you could use whatever you have on hand, too! The heavier papers are just great because they are intended to take wet paint and don't warp.
I'm a huge fan of Golden Acrylics, especially their Heavy Body and Open lines. For this, I watered down some Heavy Body paints in a few colors (putting a dab of paint and slowly adding a little water to make an opaque puddle of rich color). For stronger color, add less water! Children's acrylic paints, like this acrylic paint set, tend to be very affordable and would work well, too.
These aren't available on Amazon! :) Head outside, and take along your wide-eyed curious kiddo(s) if available, and clip whatever looks like it might have an interesting shape or texture. We picked some leafy sprigs, a Forsythia branch, small bunches of flowers, and bits of evergreen. It's best to get a variety, so you can experiment. Some will turn out beautifully, some might not - and the least expected might surprise you!