E.g. in the UK on Amazon an Arduino Uno R3 is £39.99 and a clone with excellent reviews is £6.99.
For £5 I can get an ESP8266 on a NodeMCU board - these have more GPIO, much faster CPU, WiFi, drop nicely in to a breadboard, etc. They work with the Arduino IDE with only a tiny bit of configuration.
For not much more there's an ESP-32 which adds, among other things, a faster dual-core CPU and Bluetooth.
I started out with a board from Adafruit: https://www.adafruit.com/product/2471
I later switched to this one for cost savings: https://www.banggood.com/Geekcreit-Doit-NodeMcu-Lua-ESP8266-...
I don't like having blobs on my laptop much less in MCU firmware.
I have good experience with RobotDyn's Blue Pill boards. They have the correct pull-up resistor value and a micro-USB connector that is properly attached to the boards. They also sell them with the stm32duino bootloader pre-flashed, so that you directly use them with stm32duino (Arduino for STM32) without ST-Link:
https://robotdyn.com/catalog/development-boards/stm-boards-a...
[1] https://embeddedtronicsblog.wordpress.com/2018/12/29/fake-st...
Unfortunately, many Chinese manufacturers 'improved' the NodeMCU design. The so-called NodeMCU v3 boards are two wide to leave a free row of holes on both sides. (NodeMCU v3 is a bit of a misnomer, since the NodeMCU project never made such a revision).
I like the WeMos D1 Mini boards more [1]. They have fewer pins, but are narrow enough to leave a row of holes on both sides of the breadboards. Moreover, they have a nice collections of shields that you can stack on the D1 Mini [2] and/or a base doubler so that you can put shields side by side. My favorite is the protoboard shield that costs very little, and can be used to make your own shields [3].
The Wemos boards are priced in the same ballpark as the NodeMCU ($3.50 from Wemos/Lolin). Be sure to buy them directly from Wemos though or a reliable distributor from the west, there are a lot of fake Wemos boards with bad voltage regulators, etc.
Still hoping that they'll make a shield ecosystem for their ESP32 boards some day.
[1] https://wiki.wemos.cc/products:d1:d1_mini
[2] https://wiki.wemos.cc/doku.php#d1_mini_shields
[3] https://wiki.wemos.cc/products:d1_mini_shields:protoboard_sh...