An alternative which I subscribe to is Hackerboxes[0]. It's a bit cheaper at $44/month and each month's box comes with all of the required hardware. You can check out the instructions for past boxes here[1].
I've followed both thimble.io and Hackerboxes prior to launch and thimble.io definitely has more thorough instructions and a nice learning platform[2] which may be less intimidating for beginners.
I ended up going with Hackerboxes because the kits include all the parts, use of open source hardware, the lower price, and they've already shipped a year's worth of kits.