Comment by guitarbill

I'm a fan of the RP2040 chip. It's a good trade-off between being simple and capable. There are more powerful chips like the STM32's, but frankly there are too many variants and their data-sheets are nightmarish. And there are simpler chips like the Atmel AVRs, but the tooling sucks. ESP chips are also good, but I haven't kept up with them so can't give much advice.

You'll want a dev board, which has the chip plus some supporting components on it. The Raspberry Pi Pico is a good choice because it's so widely used and well documented.

If you care about Rust, you'll also want to get the Debug Probe. Worth the money.

If you don't care about Rust, any Adafruit dev board should run CircuitPython, have good documentation, and likely some projects you can start with. The reason I don't recommend these for Rust is because many of their dev boards do not "break out"/make available the connections for a debug probe.

Edit: Having a project you want to do is good, but just making an LED blink can be magical, too, especially if you haven't done anything with hardware.