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.
In Act One, Scene 1, Bassanio has a discussion with Antonio where he informs Antonio of his financial struggles. Bassanio admits to Antonio that he has been living well above his means and is in debt to multiple people. Bassanio then explains to Antonio that when he lost an arrow as a schoolboy, he would often shoot a second arrow in the same direction. Bassanio would then follow the second arrow closely and end up retrieving both arrows. Bassanio relates this childhood story to his present situation as he describes his plan to acquire enough money to solve his financial issues. Bassanio tells Antonio about a beautiful woman named Portia who has inherited a large sum of money. Despite the fact that Portia lives in Belmont and has many suitors, Bassanio believes that he can win her heart. However, Bassanio knows that he cannot afford to travel to Belmont and approaches Antonio about financing his trip. Bassanio plans on overcoming his financial obstacles by borrowing money from Antonio to travel to Belmont. He then plans on marrying Portia and becoming wealthy enough to pay off his debts.