A couple...
1. buying a cheap or junk bamboo rod just to get into bamboo is not a god idea for a lot of reasons...
2. Bamboo, especially varnished bamboo rods require much more care than a graphite or fiberglass rod. If you are not the type of person who is willing to give your bamboo rod the extra care it requires & deserves, stop at #2. 😉
3. If you never fished bamboo, the weight is the first thing that will smack you in the face. For that reason I'd limit length options to 7'6" and shorter.
The problem with narrowing down your choices is shorter bamboo is more desirable so more expensive and a LOT of the less expensive "trade rods" are longer.
However, there is nothing wrong with 8'0", 8'6" or even 9'0" bamboo rods, I own several and fish them regularly, but I can count on one hand how many guys I see besides me fishing bamboo that length. I really doubt most newbies to bamboo would embrace those longer rods enough to justify their purchase.
4. Forget the 2wt, 3wt or even 4wt world of graphite and expect to be fishing with a 5, 6 or 7wt rod and NOT loosing any sleep over that.
5. If you don't own any reels with a stated empty weight of at least 4.5 ounces, expect you will also be considering a new reel.
6. You can use any modern plastic fly line with a bamboo rod, "older small guides" be damned. I own bamboo rods over 100 years old and a couple 70+ years old and until recently I never used any "special" lines.
7. A one tip bamboo rod will cost less than a two tip rod. However a spare tip is nice to have.
8. Impregnated rods usually cost less than varnished rods and require less TLC.
9. There are a LOT of imported rods out there on the cheap on eBay and other places that MAY suit your tastes but IF you don't like them, you will probably take a hit on the resale market and may end up SOL if you need a repair.
10. Among other rods, I own a bunch of older Orvis bamboo rods. One huge advantage to an Orvis is they are impregnated, they made a TON of rods so the prices are lower, they made one tip and lower grade (but not quality) rods that are cheaper, used rods for sale are all over the place AND you can still get factory repairs & refurbishment.
Feel free to PM me any questions and good luck!!