Hello, I can provide visual examples later if needed.
But some basic advice for simple shading is
-Use a multiply layer to apply shadows
-Consider where the lighting source is, this will help you place shadows.
-Do not shade with grey/black, if you are just starting out, I definitely don't recommend this. It gives a dull, muddy look.
-In choosing colours: play with hues instead of the tones of the colour (slide along the colour wheel instead of exploring the square part of it)
-colours next to each other on the colour wheel generally work pretty well as shadows (green-shade with bluish green, red-shade with purple, etc.)
Good luck!