Android here as well, and I haven't purchased a lot of apps either.
I spent $3.99 on IP Cam Viewer a few years ago, and it was well worth it for keeping an eye on my home cameras. I also spent $4.99 on the Moon+ ebook reader last night for my new tablet. Great app, and something I'm happy to pay for. Other than a few 99 cent kindle books, that's all I've ever purchased. I still have $10 left of free Google Play credits from purchasing the tablet and no idea what to spend it on.