The Tutorial Missions are the best place to start and can be completed at your own pace. 

You’ll be prompted to go through the tutorial when you first enter the launcher, and they will provide you an understanding of the basic mechanics of the game.

You can also choose to “skip it for now” if you’d prefer to dive in head first, they will always be available to complete later. It’s worth keeping in mind however that each completed tutorial mission will award a Core Set pack!