I was able to ramp up my team in two ways. First, it was pointed out to me that you get substantial bonuses for collecting all of the cards for individual teams. So, once I had slowly built up 15k or so coins, I went on the market and bought all of the cards for one of the AHL teams, which gives a 15k coin bonus. Then I immediately sold all of those cards, making back my initial investment plus usually some profit. After that you can keep doing that as much as you like, though I finally stopped because it got annoying.
The other thing that happened is that I had the fortune of pulling a Zach Parise Hockey Fights Cancer card out of a pack. I played with him on my roster for 50 games or so and he never had quite the impact that I wanted. I sold him for 160,000 coins and used that to buy Lucic, Kopitar, Skinner, all 3 Staals, Semin, and Mcdonagh, and I still have 75,000 left over.