PaulRB:
Buy only "breadboard compatible" components wherever possible. In other words components that plug directly into the breadboard. So Uno & Mega are out, in favour of Nano, Wemos, Teensy etc.
My common observation - take it or leave it:
The UNO and Mega are toys - designed for demonstration purposes used either alone or with whatever limited function the matching "shields" offer.
Not for breadboarding/ prototyping/ real-world applications. A Nano/ Pro Mini/ Leostick etc. will not only mount on a breadboard, but can subsequently be used as a "daughterboard" on your custom PCB, or a "terminal adapter".
For Wi-Fi functionality, move from the ATMega Arduinos to the ESP8266, particularly the WeMOS D1 Mini. Same comments apply, as in PaulRB's illustration.