There are several different themes you might address in a critical analysis of Act I of Shakespeare's The Merchant of Venice. Perhaps the most obvious are the two related themes of usury and Judaism and their role in Venetian commercial society as imagined by Shakespeare.
In the late Middle Ages and early Renaissance, usury, or lending money for interest, was regarded as a sin by the Roman Catholic Church. Since wealthy merchants often needed loans and Catholics were forbidden by the Church from providing them, the sin of usury was, as it were, outsourced to Jews at this period. This created a vicious cycle, in that the sinfulness of Jews was held to explain why they committed the sin of usury (and why it was acceptable for Christians to benefit from that sin) and the act of usury was taken as evidence that Jews were sinful. In a sense, though, for every lender there must be a borrower and thus the Christians who borrow from Shylock are obviously complicit in usury. Shylock points out this hypocrisy in the following lines:
You call me misbeliever, cut-throat dog,
And spit upon my Jewish gaberdine,
And all for use of that which is mine own.
Well then, it now appears you need my help:
This should bring your analysis to evaluation of the character of Bassanio. His indebtedness, and desire to win the hand of a wealthy heiress, drives the usury plot. As you analyze the play, you might consider whether Bassanio is as much of a villain as Shylock and that it is only religious and ethnic prejudice that makes Bassanio a romantic leading character with a happy ending and Shylock a suffering outcast.
Your final step in analyzing this part of the play should be investigating the role of the women in the play, who are introduced almost in parallel with Shylock as persons to be used by the men to obtain money.