Yep, you can buy separate ones for each topic eg. Space in Physics then Motors as a separate folder, to keep them thin too.
Then take a night off partying and sort your notes out in order of
dot points. Put them in their places... you can number your pages if the section's complete and put a contents page in front.
If you're using the plastic sheet folders, then try to slot a dot point or a section into each. If you use some sort of other ones, then your choice...
One tip is to order the section you are doing right now
backwards (at the front of the folder) so that you slot the stuff you just done in class straight in front (assuming your teacher does them in order of dot points). You can then flip it around after you finish the topic.
Writing pads go in a separate compartment.
Pracs in a different folder.
As for economics, history and that I have no idea. Ask someone else.