The range of levels varies in between each set and the length depends on how long it is until the next set release in days. It has two parts, the free track and the premium track called the Mastery Pass which you can buy access to. MTG Arena has a seasonal leveling reward system that resets with each new set.

Is it worth it? What are the rewards? Is it possible to reach level 100 from level x? This article covers all topics of the Mastery Pass.