Jay... Tenkara is actually more versatile than folks realize... I have caught from my float tube up to 26" trout with my 13'6" Tenkara USA Amago ($180)... a good starting length is around 12' to 12'6"...this will do in most small to mid sized streams... the general rule is use the longest rod possible given river/shore conditions (open to tree lined shores)... I have not had a chance but my Amago would be perfect for the Deschutes redsides around Warm Springs and Maupin using 18 to 20' of line ... of course smaller mountain streams are usually a sweet spot for Tenkara...
How much to spend to try it? I would say a $100 rod would land you a decent 12' rod... realize--no reel, just 12 to 14' leader, 4-5' of tippet and just a few fly patterns (wet/dry) often using the reverse hackle fly(referred to as "sakasa kebari" pattern)... no match the hatch pressure as your fly presentation with minimum line on the water is the key to Tenkara styled success and attracting fish...
To review a large array of rods of various costs and sizes, on the web, check out Tristan @ Tenkara Addict...he has a video where he reviewed this January his arsenal of 12 or 14 rods... Other great websites include Tenkara USA (Daniel) who pioneered Tenkara in the US (I own 3 of their rods--Amago, Sato, and Rhodo--$170 to 250), Tom @ Teton Tenkara (he has great reviews of T rods--probably the best reviewer) is another great blog/video resource, and finally, check out Tenkara Bum--with great articles and guidance on all things Tenkara and beyond... those sites will really get you the info you need to decide (p.s. local vendors are limited, best to deal direct with T rod companies)
Finally, know that for 3 years now I have only used my Amago on lakes from my float tube and have been equally successful vs past use of my Western rods... bottom line, I have found Tenkara simplifies my approach with presentation and flies... takes very little practice to "cast" 15' of line (kids can pick it up in 15 minutes), but presentation and keeping the line off the water and floating and/or sinking your fly is the trick, magic, and charm... it is "so simple"... and productive immediately... yeah, I am a believer... if you have $100 bucks or so, do some research, call any of the Tenkara vendors and discuss your "price range" ... they are a gracious, friendly, and informative group... not to go wrong...
Happy researching...let me know what direction you choose to go... would definitely encourage you to try it...you may get hooked at its simplicity and elegance...