Begin with a circuit you can explain
Learn to identify supply, ground and signal connections. Understand what an input measures and what an output can safely drive. A button and LED are useful because their states are easy to observe.
Alongside this, practise basic C program flow: values, conditions, functions and loops. Keep each practice program small enough to trace on paper.
Add one peripheral at a time
After digital input and output, explore a timer, a serial output and an analog measurement. Write down what each block is meant to do before coding. If several unfamiliar peripherals are introduced together, debugging becomes guesswork.
Use the exact board documentation for pin assignments and voltage limits. Example code is a starting point; it is not evidence that your wiring or board variant is correct.
Build a small complete system
Combine a sensor reading with serial output or a display. Then add storage or connectivity only when the basic measurement behaves consistently. A modest system with clear test results teaches more than a long list of unfinished features.