the last one is awesome.
some tips:
- use pathfinder to crop lines and shapes inside other shapes by duplication and intersect.
- take a good look at width tool, you can make it more stylish and acceptable changing line width.
- dont rush your pen tool, always keep everything fluid, a tip is to use the anchor tool to smooth lines.
- make forms without contour to make shadows and light, you can use gradients on those for style.
the rest looks fine, I recommend you to experimenting with mesh tool to make gradients with more control, in some cases it is necesary.