Node MCU

This is the recommended board for beginners that want to learn more about electronics and programming!
External PICTURE NodeMCU v1.0
The NodeMCU is an open source project and there are many companies producing it. The most known one is Amica. There is also a Lolin NodeMCU v3 but don’t get confused by any version number:

PICTURE NodeMCU comparison

I always recommend the v1.0 (might be sold under a different version number). It’s the board from Amica. It is cheap, breadboard friendly and uses the cp2102, a better alternative to the old CH340 USB to serial chip.
Please note that the quality of those boards can vary a lot! They are produces very cheap and you can get them for around 3 - 5 USD from AliExpress and other Chinese based sellers. So don’t pay too much for them!

There is also this NodeMCU inspired development board by DSTIKE:
It has a LiPo charger on-board and allows you to connect an external antenna for better range.