> I bought an Arduino board (sorry if that's totally kiddie to you)
Not kiddie at all, AVR microcontrollers have been used commercially for ages and they have some properties that can be nice, e.g. they are fairly simple cores, they operate at 5V and their output pins can sink ~40mA, so you can easily e.g. drive a MOSFET gate.
The Arduino ecosystem is huge and it's great to get things up and running quickly.