Analyze the theme of "outward show" in Bassanio's speech in act 3, scene 2.

This question is asking you about Bassanio's speech which begins, "So may the outward shows be least themselves." Quite evidently, the theme of "outward show" is very prominent in this section of the play. Your task is to identify the language Shakespeare uses to communicate this theme and also to explain what is being said about it. What does Bassanio's opening statement mean?
If "outward shows" are "least themselves," what Bassanio is saying is that what we see on the outside—particularly on the outside of something that has been made deliberately showy and gaudy—may not at all reflect the inside of someone or something. Indeed, it may reflect the exact opposite. This is important because, Bassanio says, the world is "deceived with ornament." People will look at a beautiful thing and determine that it must be a good thing, even though this doesn't necessarily reflect the truth.
Bassanio returns again and again to this idea throughout this speech: he is fixated on the idea that "grossness" can so easily be hidden by "ornament" because of people's perception of beauty as being equivalent to goodness. There's a lot of mercenary language in the speech, too, suggesting that beauty is something that can be "purchased"; words like "golden" reinforce this theme. According to Bassanio, those who are beautiful are "lightest," even though beauty can often be "the guiled shore / To a most dangerous sea"—that is, outward beauty can actually just be a means of luring someone in, after which it will be determined that what is inside is actually very treacherous.
Bassanio goes through this reasoning to eventually determine that "meagre lead" will be his choice, because there is no effort made on the outer face to lure him in. Therefore, he thinks the content of the box is more likely to be what he really wants.
You can also think about how the themes of this speech are reflected elsewhere in the play, if your question allows you to go beyond the speech alone. Who is beautiful in this play and is seen as good, without really being so? Who is "ugly" and therefore immediately determined to be morally bad? And how do the outward shows people wear sometimes mislead others? (Think about Portia later in the play.)