Suggest browsing sites like Adafruit, Makershed, and Sparkfun. They all sell experimenter's kits that include an Uno and a booklet of experiments, and the necessary components. But you already have an Uno. OTOH, there's not a lot of downside to having two! The booklets for the aforementioned kits are online as well, so you can see if they interest you in advance. Or you could pick-and-choose experiments from them. Depending where you are, and what your local electronics store is like, you may be much better off online. The sites I mentioned are well worth supporting, and there are lots more where they came from, GIYF. Check out the modules and sensors they have available, pick up a couple that look interesting.
Welcome to the cult, hope you have fun!