Contrary to what you have been advised so far, get a small coil, assuming you have the funds you are willing to use for that. The small coil will allow you to learn faster I think, as the signals will tend to be more isolated, and not compromised by as much trash. I hunt mostly older homes as well, and they have a lot of junk in them it seems, at least in the area I live. Learn the machine's response to different environments, and then, learn again. Go SLOWLY and listen to the fainter sounds. The 5 inch is known to be a great separator of signals, and you will learn to tell the sound of trashy iron, nails, coins, etc. Of course, I would dig everything for a month or so, as I express to everyone. Depending where you are, it is good to dig everything in some places regardless......
For my arsenal, I use a WOT, the 10.5 inch, the 5 X 11 Elliptical, the 8 inch, and a 5 inch coil. EACH has it's place. Of those listed, I use the 5 inch, then the 8 inch, then the elliptical in terms of frequency of use. As a full disclosure though, the older homesites I hunt usually are scraped lots in an older part of town. Lots of trash, lots of treasure as well. The larger coil will average the signal some. With the small coil, I still get a sweet note out of the middle of trash it seems. Lately, I have found a Virginia Staff button, and a really neat token right in the middle of a bunch of trash, due to the sweet tone which came through.
HH
Dennis