Any recommendations on best transportation from Florence to San Gimignano?
Bus (with a change at Poggibonsi)
First bus 131 from Florence to Poggibonsi
https://www.at-bus.it/en/linee-e-orari/regionali-131
Then bus 130 from Poggibonsi to San Gimignano
https://www.at-bus.it/en/linee-e-orari/siena-extraurbano-130
You can also reach Poggibonsi via train but it takes a little bit longer (train Florence-Siena, but get off at Poggibonsi, about half way.