Adafruit Circuit Playground Express - A great board with TONs of toys built in! You can really jump straight to programming all kinds of legit projects without connecting anything else to this board! When you do try soldering, the big pads make it easy, and you can even make temporary circuits with alligator clips. It uses Arduino, Circuit Python, and even the super simple Microsoft Make Code languages.
Adafruit Trinket M0 - Cheap (less than $10), TINY so it fits in your project, uses Circuit Python or Arduino languages, and has a multi-color LED and touch switches built in so you can try some programming without adding anything.
Arduino - The most common, and most powerful microcontroller language. It is based on C++, and so can sometimes be hard to read, but things you learn here can be directly applied to programming on PCs, game consoles, and other things! Don't worry, you can also do lots of powerful projects with very simple commands too! The original Arduino site, linked HERE, has lots of good lessons and references!
CircuitPython - A scripting language by Adafruit that is easier to read, and easier to load on your microcontroller! No fancy software is needed, just a text editor! You simply drag your code onto the microcontroller, that shows up as a USB drive! CircuitPython is based on Python, which is a scripting language used on the web, and on many different devices. It is somewhat new, so you'll have to start with the overview on Adafruit, HERE, and then look for beginner resources for general Python, like THIS ONE
Microsoft MakeCode - VERY EASY! Just slide icons of blocks together on the website to make a program! The general getting-started guide is HERE. Then you can find the editor made specifically for the Adafruit Circuit Playground Express, mentioned above, HERE. There's even a built in simulator, so you can try programming without even owning a microcontroller!