Since some of our group tours start from Mestia while others start from Tbilisi, here are our recommendations.
The most preferred option is the train. You can buy tickets on this website. Train will get you to Zugdidi(6 hours). From where you can take the bus or share the minivan (3 hours until reaching Mestia). It is easy to arrange a private taxi from Zugdidi bus station and there is no need to book it in advance.
You can also get to Mesia by plane but you need to buy the ticket 1 month before the fly and the departure of the plane is not guaranteed.
Private transport: We usually arrange transfers but it can be expensive with experienced and good provider. It can be an idea to get a cheaper regular taxi via taxi apps however we can not guarantee your happiness with service provided. In any case it's not worth spending this much money on transport to Mestia and sitting in the car for 8 hours. Also, it is worth mentioning that traffic on highways and Georgian way of driving (by other cars) can be a bit of culture shock for a guest.