@jayemel: tempered glass works perfectly, as the (theoretical) fluctuations in flatness as a result of inner stress are several orders of magnitude smaller than the significant variations of thickness of your sandpaper. Unless you want to reflect the light of distant galaxies off the bevel of your chisel and measure their red-shift, you will be fine (and safer) to use tempered glass.
The fourth most important basic handheld power tool every beginner should buy is a random orbital sander. While palm sanders are less expensive and can use plain sandpaper (cut into one-fourth sections), the random orbital version uses hook-and-loop fastened sanding disks, and doesn't sand in patterns, using instead a random sanding motion. This will motion will serve to reduce the chance that any sanding marks may appear on the stock due to the sanding. Of course, be certain that your local woodworking supplier has sanding disks readily available in a number of grits to fit the model that you choose, as the key to proper sanding is to use progressively finer grits as you sand to reduce or remove any marks that are left behind from the previous sanding.
The best advise I can give you is to get and read the book "Hand Tool Essentials" by the staff of Popular Woodworking before buying any tools. It is sort of an inexpensive crash course in hand tools. Chris Schwarz's book "The Anachrist's Toolchest" is another good source of information on handtools that I found to be a fun read. Use the internet to learn all you can about a tool before buying. The tools you need are dictated by what you want to build.
Sadly, that’s most of my power tools and shop accessories, but it’s a growing collection. Compared to all the money I’ve wasted on small electronics and computer junk in the past, I’d say this has been, and will continue to be, a much better investment. I just wish I had come to that realization back in college, when I was probably spending $500-$1000+ a year upgrading my computer.
A layout square, or combination square, comes in 6” and 12” sizes. Most woodworkers use the 6” model, simply because it’s easiest to carry around. Also, most of the stock you’ll use will be no bigger than 6” wide, so 12” is overkill. The layout square is a triangle that you can use to mark square cuts on stock. Once you measure the length of the cut, you line up the layout square with the edge of the board. The short side will give you a straight, square cut across the end grain. You can also measure off angles with the layout square. This helps when you’re trying to measure for a bevel on a table saw, or marking a cut for a miter saw. You can even use your layout square to determine an existing angle. Just be sure to buy one made of metal. The plastic ones are not only fragile, but they also can warp, making them pretty useless.