If you are willing to put in a bit of time, start using the community market to flip cards. For example, most Diamond sponsorships and a lot ofgold players can be bought (buy order) for just over 1000 stubs and sold (sell order) for around 1800 stubs, giving you ~500 stubs of profit after the tax. Even with a mere 15 mins once or twice a day you can make a lot of stubs (at least 10000 per day) this way with no risk.
Also, do the player programs for the 5th, 6th and 7th inning. They will get you program points and some solid players. The Topps now moments lead to packs with very high diamonds in them that you can get relatively easy. Combined with the shark map, you can get an all- 90+ diamond team within a day.
Have fun!