Let's go back to the beginning anabol. Asking us to compare junk pots is like spending hours deciding whether to eat at Burger King or McDonald's.
You said you want to explore the Yixing "clay experience" as you put it, but truthfully that could mean a whole ton of things. The chances of finding a $30-$50 pot these days which is a keeper that you'll want to cherish and continue to use, season, and take care of for years to come is sadly very small indeed. That being said, finding a pot made from real clay in your price range that will introduce you to the world of Yixing, and get the ball rolling on your experience and education is quite doable. Rather than have the forum respond to a myriad of links to ebay and such, it's probably better off to give you some basic guidelines:
1) For your first pot, stick with the two basic colors of clay- red or purple. Stay away from black, blue, green as these in your price range will almost certainly contain additives to achieve their color. You can look at yellow (duan ni) pots if you wish, but personally I don't think most of them do great things for a tea's flavor and aroma.
2) Stick with a basic, plain shape. Avoid engraving and painting on the side, and definitely avoid pots in the shape of animals or other stuff.
3) Ignore all claims made by the seller. In fact, don't even read the description in the ad, aside from finding out what size the pot is. Just look at the shape and the clay and decide if you like it, and if it looks like pure clay without "makeup clay" painted on the outside surface. If the site doesn't have sharp photos that show the clay's detail, avoid it.
4) Look for clay that has slightly sandy texture, and is not too shiny, and not too dull. (Takes practice, I know).
5) When in doubt, go buy the pot I recommended, cause I've been at this for 5-6 years now.
If nothing else, you'll get your feet wet, begin to learn, and you won't be throwing your money away on a piece of crap.