Learn to sew. You don't have to be so good that you do intricate quilt work or make all of your own clothes. If you just learn some sewing basics you can save yourself a whole lot of money (or at least a lot of little expenses here and there).

The strap adjuster on my son's backpack broke the other day. Using my
seam ripper (the most important tool a seamstress can have) I was able to remove the old piece and sew on a new one. It took me about 45 minutes. I only needed to know how to stitch forwards and backwards. For all of you who are trying to think about how much money I saved, here is a conservative estimate:
This backpack new (but on super-duper clearance) = $3.50
The
new plastic piece (it comes in a 2-pack) = $1.29 for 2
So, even if I could find another cheap backpack, it would still be cheaper to fix it myself.
Now, don't even let yourself think that I have some great expensive machine. I don't. In fact, I have the
cheapest [adult] machine that Target has to offer. It works great! The machine I had before the one I have now was not so great so if you are looking to buy
don't buy
this one. It is also important to remember that sewing is more forgiving than you might think. If you look inside of some of the things I have made you would be amazed at how great it looks from the outside.
Sew, go sew (if you don't know how, I am sure that you can find a friend who will give you a hand).