The reason some people use a circle is because that leaves no place for the chicks to pile up and squish one another like they can do in corners. That said, I would say that most people use rectangle and square brooders without any problems. Chicks tend to pile in corners when they are cold so as long as you have the temperature correct and give them space to get away from the heat if they want to, you should be fine with a rectangle or square brooder. You can go to a grocery store and see if they will give you one of the big cardboard bins that watermelons and other fruit comes in. They make good brooders but you may have to cut down the height some so you can reach the bottom to change whatever bedding you use. The last couple of years, I've used a Grand Wardrobe box from Uhaul ($11.95). It comes with a bar (for hanging clothes) which is great for hanging the heat lamps from if you are going to use one of them. Regarding the small quart size feeders and waterers made for chicks, I use them. They last forever so when the chicks outgrow them, I just store them for my next batch of chicks.
Good luck with your chicks!