I'm pretty new to microscopes too, so I'm at the same sort of stage. What I did find useful was to go on ebay and buy a set of prepared slides - which meant that I got ~50 different things to look at (fly legs and other insect parts mainly). It was a really fun way to start off learning how to use the microscope. I also bought a pack of blank slides, tweezers and glass covers, so that I can start to find things to make my own - the first will probably be lichen
.
You've got me thinking about this now, so I'll try and get back in to it this week
. If I manage to see any tardigrades, I'll post some pics on the forum.