Depends on what you want to spend. There's a number of good standard def receivers, you should be sure you get one with blind-scan feature, most of them have that these days. A lot of us have several, start out with one, try another for different features. They're a lot like computers, after awhile you want to upgrade, newer boxes sometimes will have improvements you really want to try, etc. So far there's not a lot of full-time HD on KU band, which your primestar/channel master dish is, so I won't try to recommend an HD receiver. A lot depends on what you want to see, you'll find some wildfeeds, newsfeeds and some sports events in HD, but I'd say start out simple, get yourself familiar with fta first. The next thing you'll want is a motor, so you can move around to the different satellites, and sample everything. Look at our review section to read about users experiences with some of the fta receivers out there. If you can land a Coolsat 5000 they're probably one of the most popular, but they're not made any more. ebay, craigslist has them from time to time, if you trust shopping that way. Fortec Mercury 2 , Traxis 3500 are a couple of other simple boxes that do a good job blind-scanning. There will be lots of opinions, like car-shopping!
EDIT: Now, for my personal opinion, the best one I've found is the one I'm using most>Icon S550 (brother of the Satopia, same receiver). I own the others I mentioned above, but the Icon is the best all around SD receiver I have found. FAstest scanning, super-sensitive tuner, and will display most any channel it finds.