Why does Bassanio set his sights on Portia in The Merchant of Venice? What stands in his way? How does he plan to overcome tose barnies?

Bassanio would appear to be a bit of a chancer however 'nice' he might be as a personality. He has already squandered a lot of Antonio's money on some unspecified failed venture and now he's embarking on another very risky enterprise which depends on a lottery. He seems to have no gainful employment and spends his time with other men-about-town doing nothing very productive. His attempt to win Portia seems to be purely financial - he refers to her wealth in his very first mention of her - and designed to improve his own position. However, as with any business venture, he must put out money to gain money and presumably he must put on a good show of wealth to get anywhere near Portia, which is why he borrows so heavily from Antonio. The other two suitors are wealthy aristocrats, so obviously not any Tom, Dick or Harry is allowed to try the casket test. The real mystery for me is why the astute Portia doesn't see what a chancer Bassanio is under the show of wealth. We are told that she has found him attractive in some previous encounter but he seems a rather bland 'catch' for such an intelligent and dominant lady as Portia appears to be.