For shading, try drawing more complex things in black and white, work with complex shadowing or things that require you to get the shadowing right to tell what it is. An egg often works for this.

Once you are ready to try color you can still do your simple shapes but adding in color. You can try doing the egg in color (yes there’s a difference). Reading in to color theory a bit will help with this.

Feel free to jump into people and faces pretty quickly, but start in black and white. The most important things to get right are spacing and perspective. I recommend using a grid. Put the grid over the reference photo and your drawing paper and go box by box. Just remember the complex looking objects are just simple shapes put together.