Personally I think it would be better to just buy cards that you see well below market price and do a quick turnaround rather than sit on a bulk of cards. You'll have more clintz available to make larger purchases to profit on and you won't have to wait for that bulk to sell.
Smart small term investments.
Scotty Ld's picture got leaked. We could tell he was in rescue due to the mark on his eye. (durrr)
Every Staple goes up due to Scotty Ld's release, what do we do?
Buy 30 Kerry's.
Wait until it was announced.
Personally I don't like the 'quickturn' suggested by RG, theres far to many people doing it and getting a card cheap enough to make profit on is rare with all the scopers on the market, its good when it happens but meh.
Short term investments generally work to be fair, theres still a good 15 clans that legendary cards haven't been announced yet so I would just go buy a multi copys of a staple in 1 clan thats cheap and wait.
Getting rich doesn't come in 1 day unless your willing to buy credits.