By completing the daily challenges (5 stars each) every day, you'll gain 28 tiers (as you get two challenges per day and each tier is 10 stars), any further will depend on how much you level your account. You get 1 star for each level, or 5 for every 5 levels and 10 for every 10 levels. For an increase in 50 levels (a significant amount of playtime...) you'd gain 11.5 tiers on your battlepass. So realistically, you're only going to get 30. I'd play like a beast, making sure never to miss a day and buy the "10 battlepass tiers for the price of 6" that's currently on offer.