Hi Bill,
There is a resources/FAQ page for the 3800 that may help you get started.
http://people.csail.mit.edu/ericchan/dp/Epson3800/index.htmlhttp://people.csail.mit.edu/ericchan/dp/Epson3800/faq.htmlYou can look at the Ink Usage question to get an idea of what inks tend to go fastest, but I will warn you ahead of time that it depends not just on what paper you use, or whether you shoot landscapes vs. architecture, but rather on the mix of colors in the palette. Warm colors (e.g., fall colors) lead to very different usage patterns than cool colors, as you'd expect. That said, the fastest ones to go are usually Light Cyan, Light Magenta, Light Black, and Light Light Black. If you're printing lots of warm colors, Yellow could be up there, too. Cyan and Magenta (non-Light) go slow. Cyan will probably take the longest. Regular Black is somewhere in the middle.
Unless you're printing a lot, I wouldn't buy too many cartridges in advance.
On the above page you can find other papers available in 17x25.
I have had success using both USB and Ethernet, but some users are reporting having trouble with getting bidirectional communication working with the Ethernet. That is, they can print, but they can't get status information back. I have noted this in the FAQ as well as noted my personal network setup in hopes that it will help people, but at this stage I don't have any advice to offer here except that you have to try it and see if it works ...