Firstly. You do not aim to be verbose. Verbose is a negative term used for people who try to be literary.
Secondly. You don't aim to use good words, you aim to use the right word at the right time.
For example:
Virgil presents Aeneas as a human character, rather than a strong hero.
In the above sentence, I could say:
Virgil presents Aeneas as a credible human character, rather than a pale paragon.
The word paragon, I learned recently means 'an ideal embodiment'-like a hero.
So the trick is to use the right word in the right context.
If you try and use words you don't know well enough, then you will get far worse marks than if you were to use plain simple english.
To expand your vocabulary in an effective way, read Literary journals on the books you are reading: these can be accessed off JSTOR off the State Library Website.
Also make a book of all the 'good' words you learn, and provide an example. I have had a book since Grade 1, which I, till today add words to.
Most importantly, don't let the need for good words or quotes detract from what you are trying to say in an essay.
Read some of pooshwaltzer's posts, they are like essays in themselves-look up the good words he uses.
Cheers.