To see the best of Chianti and more of it in a single day, you really do need hire someone who knows the area well. That’s expensive I know, so here’s a cheaper way to go about things.
Fortunately at least one scenic Chianti wine road the “Chiantigiana,” is served by bus line. You can catch the bus at the main bus station in Florence (near the main rail station). The line to look for is the 365 for Gaiole - Castellina - Panzano - Greve (via Ferrone/Strada) - Firenze. You’d be best going directly to the station for times and info, as their site (Bus Italia Nord) seems to be in Italian only. However there is an on line timetable if you know Italian.
It's a pleasant trip of about an hour from Florence to Panzano, which is where I suggest you make your first and southern most stop. Take a walk up the steep main street of the village to a delightful enoteca (wine shop) called Accademia del Buon Gusto (Piazza Ricasoli 11, +39 055 856 0159). A great wine tasting is available "without obligations". The owner Stefano Salvadori is a knowledgeable host, an expert on wines, and last but not least, quite a character. You’ll have a fun time and you'll probably end up buying something anyhow, but it needn't be expensive. For lunch you may like to try Dario Cecchini the Butcher's fast food joint. Dario Cecchini is another lively character who’s made a name for himself with the Chianti Hamburger. My opinion? Well it’s a huge hamburger, but why come all this way to eat a hamburger. I’d go for Tuscan home cooking at La Cantinetta Sassolini which just opposite the Accademia, mentioned above, or Oltre il Giardino near the main road. Just ask you can’t miss either of them. If you choose the suggested light lunch menus, you'll dine inexpensively too.
To walk it all off, take the village street up to the church and follow it round to the left for some splendid views over the Conca d'Oro (Golden valley), one of Chianti’s most picturesque areas. Now take the bus back to Florence and Greve in Chianti the capital of Chianti Classico, and browse the arcaded piazza and a wine shop or two. You might also like to visit the “other” butcher’s shop “Falorni,” but this one I recommend. It’s famous for Tuscan specialties such as salami, prosciutto and sausages. Take another bus north one stop to Greti, and here you’ll find the roadside tasting room of Castello di Verrazzano. Maybe you could ask the bus driver to tell you when you arrive, they’re usually quite helpful. The address is Via Citille 32, Tel +39 055 854243, and it’s along the main road. It's free to taste here, and there are affordable bottles from this fine history making estate.
Your DIY Tuscan Tour ends here and the last bus back to Florence leaves at 8 pm weekdays and 5 pm on Saturdays. Don’t bother on a Sunday. The bus fare will set you back about €10, which is a whole lot less than what I’d ask you. However if there are more of you, seven is the perfect number in order to spend the least, then for €55 you can have a luxurious day.
Take a look here: Scenic Wine Tours in Tuscany.