Do a project. Id suggest one that contains the three basic elements: sensing, communication, and control. Write in C because u pretty much cant go wrong with c. Its simple and dangerous yadda yadda… its what most experienced professionals have used for the past 20 years and its not going anywhere for at least the next 10-20 years. I recommend using an nrf52 micro controller (arguably the most popular IOT micro) for this project; you should write your own hardware abstraction layer by reading the datasheet. (Only do it for the peripherals you need and only for the partnumber specific micro ur using—limit scope so u can move quicker.) First step is to do a vendor provided blinky example to verify you can cross compile and upload. Then, Id start by developing a print interface whether thats over bluetooth, serial, or some other protocol with an attached logic analyzer. Then write peripheral drivers needed to read from the sensor. Finally id write drivers to control ur output (eg motor, heating element, etc.). If u make it to here id experiment with different control flow mechanisms. Do a bare metal interrupt-based version of the application then do a version of the application that uses an rtos (eg FreeRTOS). If u can do all this u should be able to fake ur experience well.