The phrase was popularised by Shakespeare in 'The Merchant of Venice"
It means that just because something looks valuable and appealing, doesn't mean it is worth having. Looks can be deceiving. It's similar in meaning to the more common (nowdays) "Don't judge a book by it's cover".
A good structure to your oral test could be
Origins of the phrase and it's general meaning
Perhaps how the phrase relates to modern times, with examples. Is it still relevant in today's society? If so, why? If not, why not?
Basically tie up the middle. If you think that it is still relevant, Maybe something about the powerful, universal truth in a phrase that has survived the ages.
1 minute isn't a long time to talk so you should be able to flesh that out quite easily.
The key to giving a good speech is really just practise until you know it back to front. Then you'll have more confidence so you can look away from your notes and give good eye contact, put the emphasis in the right place and sell your point :)