So I have now been playing for almost 2 months Hearthstone. Game has a bit of a high learning curve than I expected. I think the biggest mistake I made and something I advised a friend who just started playing now is to not use your arena credit right away. Blizzard is sending you out for sacrifice if you utilize it.
I would say my experience for the first 3 weeks was awesome than I hit a rut as I could not construct decks to really advance up ladder. Facing people who have multiple legendaries when you are rank 18-19 is not fun. However, after using gold for 3 of the Naxxramas sections, I bought the rest myself. It enabled me to construct a hunter and zoo deck to at least and compete on ladder. I have got to rank 10 now and have started playing arena again and have averaged 5 wins over my last 5 runs.
Overall, I think for anyone starting to play, Nax is almost a must purchase. Otherwise the grind for the game is simply too long and you do not have the knowledge to make arena worth playing at the start. With the Nax cards you can at least create an okay deck to begin to learn the game so you can play arena later. The prevalence of hunter on ladder is because of its cheap dust cost. I think Blizzard could improve the system by significantly giving more dust for disenchantment or increasing the amount of dust starting players receive.