I know it's not much. Most of what I need (Pens, pencils, spirals, etc.) I've bought from previous years when Target does their supplies clearance at the end of August. Everyone is pretty much in school by then, and Target severely discounts their supplies to get ready for the next season. I bought a bunch of stuff last year when they did the clearance, but one thing that I really didn't buy because they didn't have any of was binders, and I found so many uses for binders last year but I didn't have any. So this year, I've stocked up.
I have three 1 1/2in binders in aqua blue, black (this is for theater), and green. I got these from Target on sale for $3 a piece. The different colors were the same price as the black and white ONLY if you bought Target's Up and Up brand instead of the name brand, which I have no problem doing to save some money.
I also bought four 1in binders in black, lavender, light blue, and light green. I got these on sale at Office Depot for $2.50 a piece as well, and the Life Touch brand was MUCH cheaper than the other Wilson Jones binders that were the same size. Again, the colored ones cost as much as the black and white, but I still got a black one for theater.
Lastly, I got 2 purple 14 pocket folders from Office Depot. These things are so much better in my opinion than individual folders. All of your papers for your different classes are in one place. I don't know what I would do without them. I bought one for each semester, because they do get pretty beat up. These were not on sale, but they are my holy grail for back-to-school.
My best advice for school supplies is this: Stock up while you can and buy on sale. I may not need all of these binders this year, but I got them while they were on sale and I can save them for the next couple of years. If you can, stock up at Target when they clear everything out. You can get some cute things for MUCH cheaper than normal.
I would also suggest not getting your school stuff from just one place. I know it's easier, but you'll save money if you buy from different places. Target didn't have the 1in binders on sale, but Office Depot did. Just compare prices before you commit to buying. If you need to go to Target for something, take a list of things that you need for school and write down the prices at Target for those things. Then you can take that list to Office Depot, Staples, Office Max, Walmart, or wherever you go, and if you find something cheaper, get it there. If not, head back to Target and get it there.
Hope this helps! Buying school supplies is one of my favorite parts of going back to school, and it should be as stress-free as possible. Have fun with it, and buy yourself some fun colored binders, pens, or something that will make doing your work so much more fun!