I've spent a total of $100 over the last 2ish years playing and I have a very extensive collection. The grind does get you a lot of packs if you play 2-4 games a day, and most of my money goes to the season passes. That being said I still lose sometimes to the free basic decks that are offered out the box.

If you can complete the daily quest every day, and finish your weekly challenges every week you get a good amount of gold towards packs. I'd say you'd be meta ready in less than 2-3 months on just grinding alone. Not to mention the packs you'll get for starting a new account and all current promo offers.

If you want to jump start the current meta, spend like $40 on gems and use the gems for packs.