If you're interested in AVRs, Arduino might be the best place to start. It's around $10 for a Nano version, which can do a lot, and you'll only need to add a USB cable to get started. The libraries are technically C++, but they tend to hide the complexities of the language until you get really deep into it.
Raw AVRs are more verbose, but have the advantage that you can use a single chip for buck or two. You can get programmers for around $15-30.
They're not necessarily hard real time systems, with a bunch of rigorous guarantees about latency. But as microcontrollers, nothing is running except your code, which is usually good enough.
"There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.