Act 1, scene 1 shows a little bit of greed. Its main focus is on the wealthy merchantmen of Venice. The scene shows the reader how men like Antonio and Bassanio have money and financial success at the forefront of their thought. I hesitate to equate the scene to full on greed though, because I tend to think that the scene simply shows that Antonio's business is a high stakes, high stress business. Sure, the success of his business will gain him more money, which he obviously wants. But I also have always gotten the feeling that Antonio would like to be a successful businessman for the sake of being successful, not necessarily only the money.
Greed is better shown in scene three. Shylock is a greedy money lender. The best evidence for that is the fact that he is incensed at people like Antonio who loan money without charging interest.
He lends out money gratis and brings down
The rate of usance here with us in Venice.
That shows that Shylock is purely focused on the return of his money (plus some) and not focused on the benefits that his money will provide for people.