Hey, I've used the Stealth buyer a fair bit
For settings it's pretty simple. You want to make it look as human as possible. For delay times most people recommend this-
Find an item that is always in stock in your chosen shop, and add it to your AB list. Once it is on there start the AB and let it autobuy said item. Then in the program log you can see how fast your natural delay is, and adjust the delay times from there.
Ideally from my experience you want your total buy time to be somewhere in the 3-3.5 second range, although I'm sure people will have their own thoughts on this. So, if your natural delay is 1000ms, you need to add a delay of between 2000ms and 2500ms before buy.
Setting the AB to take a break is a good idea, how many people restock for 5 hours non stop with no breaks? I usually set it to take a 15-25 minute break per 50-60 mins, as that is what I would do if I was RSing.
Make sure you use a high anonymity proxy, personally I use the free ones at www.hidemyass.com. - go to IPort proxies and filter them down, port 80 or 8080 are the ones I use.
Avoid Magic and Stamp unless you're feeling like taking a gamble, as theyre the most ABed shops and more likely to get you iced. Don't transfer items to your main for atleast a week.
Read this thread of @Infamous Joe 's, very helpful: