And you can find an abundance of freebies which are really, really cute.
I have a sticker shop on Etsy called Grandma DiDi Designs, which I started to try to recoup some of the cost of the addiction I had acquired. But I started out, as many designers do, making freebies. A link to all my freebies is now located on the navigation menu. Help yourself to whatever you'd like. I will say my early efforts weren't perfect, and I did some pretty weird things. Some didn't fit right on the paper planners, but with digital you can resize them, crop them, or use them any way that you see fit.
The Ultimate List of Free Planner Stickers maintains a list of about 40 sites to get free downloadable stickers.
Facebook has several groups in which members create and share their stickers, and offer tips on creating your own. The largest of these is Happy Planner Free Printables to Share with over 10,000 members. The files are full of free designs, and many other designers with their own pages drop by frequently with links to their new items.
I will be adding more freebies here as well.
You can spend a lot, a little, or nothing at all.