Check out some different HO train sets here... http://www.modeltrainstuff.com/HO-Sc...Sets-s/334.htm
I do a lot of business with them and their pricing is very good and their shipping fast.
Go new for the first train set. Locomotives and such are much more reliable than they were a decade ago.
Also get some extra track, especially switches. Just watching a train go round-n-round gets boring after a while. A few places to switch cars is highly suggested.
Maybe start with a 4 x 8 sheet of plywood.
Maybe get a subscription to "Model Railroader" magazine, the "bible" of the industry.
Here's a couple pictures of my N-scale layout: