You will only need craft paper punches (any shape you like) and plain cardstocks. Here I used a flower-shape puncher and a mini-round hole puncher. You probably already have these materials at home if you love crafts as much as I do. If not, these punches usually cost $5-$10 a piece and a stack of 100 cardstocks is around $5. It's a good investment if you need a lot of notecards or if you can use the same craft punches for other projects.
This DIY is very versatile. You can chose cardstocks in any color and paper punches in any shape that you like. It's a fun way to use your creativity :)