Thin plastic hangers: They are worth the money since they allow you to hang twice the amount of clothes than if you used thicker plastic hangers. I bought a 10-pack of blue hangers at an Asian market for only $2.49. I might be a hypocrite here because I succumb to buying the thicker ones since they are a lot cheaper (only about a dollar).
As you can see, on the left the plastic hangers which I mainly use are a lot thicker than the blue ones on the right.
How to store sweaters/tank tops and pants: I fold them instead of hanging them. I could actually fit all my tank tops and pants in one shelf and sweaters have their own separate shelf.
How to store scarves: Use a plastic hanger and shower curtain rings to organize scarves. If you don't have shower curtain rings, you can simply tie the scarf onto the hanger (which is what I do, and works just as well).