Mobile operators offer very low prices in Georgia, so it's always better to buy local number while staying here. In some countries it's really hard to get a new sim card, but in Georgia it's very cheap and easy. You need your passport and about 5 Georgian Lari (2$) to buy a new sim card.

There are three main companies offering GSM sim cards in Georgia: Magti GSM, Geocell, Beeline. They offer very reasonable prices. For example, avarage prices in Georgia are listed below:
Cellular Data: 5GB - 5$
Internation Calls: 0.2$ per minute
Local Calls: 0.05$ per minute
SMS: 0.03$

To get lowest prices, you need to apply for monthly offers. You can see all offers online:
https://geocell.ge/en/private/services/tariffs
https://www.magticom.ge/en/private/mobile/packages/bundles
http://beeline.ge/en-us/tbilisi/customers/mobile/tariffs/index/localcalls/

It's very easy to activate new sim card, you don't need to go online and enter any code. All you need is to insert your sim card to your mobile phone and it's already activated!
There are many customer service centers in Tbilisi where you can easily buy sim cards. You can see this service centers on the link below:
https://geocell.ge/en/private/help-support/get-in-touch/our-offices
https://www.magticom.ge/en/useful-info/offices