In Tbilisi, Yandex Go and Bolt both work and are cheap. The metro runs on a Metromoney card that also works on buses.
Between cities: marshrutkas are the fast, uncomfortable option and leave when full. Trains to Batumi and Zugdidi are comfortable and worth booking ahead in summer.
DRIVING: a foreign licence is accepted for a limited period after entry, after which you are expected to hold a Georgian one. The rules here have tightened, so treat any figure you read online — including an older version of this page — as something to confirm at the Service Agency before you rely on it.
Mountain roads close in winter. Check before you drive to Kazbegi or Svaneti.