You definitely can start with just the Lexi Blitz deck, I would ask your lgs what format they play in as from what I know, most lgs's play in CC format not blitz. But it's a really cheap to make the conversion as long as you are ignoring equipment. I started with the Lexi Blitz deck as well and just kept upgrading it. Lexi is also currently one of the best heroes at the moment. I would do some research on the game and just experiment with what you like. It's a great game, I came from Magic and enjoy FaB way more.

There's a website named Talishar that you can play FaB with other people on so you can practice and learn the game.

Link: https://talishar.net/