If you're interested in studying English at Cambridge, we recommend that you try to read material from a number of different periods if you can, as the course will introduce you to the full range of literature from the Middle Ages to the present day.
If you want to explore what you could read from some of the earlier periods and are wondering what you might enjoy, why not spend some time browsing the Luminarium website? It's an anthology of English Literature with particularly well-developed sections for Medieval Middle English Literature (1350-1485), Renaissance Literature (1485-1603), Early 17th Century Literature (1603-1660), and Restoration & 18th Century Literature (1660-1785).
Here's a poem by Henry Vaughan (1621-1695) to get you started:
False life! a foil and no more, when
Wilt thou be gone?
Thou foul deception of all men,
That would not have the true come on!
Thou art a moon-like toil ; a blind
Self-posing state ;
A dark contest of waves and wind ;
A mere tempestuous debate.
Life is a fix'd, discerning light,
A knowing joy ;
No chance, or fit : but ever bright,
And calm, and full, yet doth not cloy.
'Tis such a blissful thing, that still
And shine and smile, and hath the skill
To please without eternity.
Thou art a toilsome mole, or less,
A moving mist.
But life is, what none can express,
A quickness, which my God hath kiss'd.
For poem and source, see Luminarium. The poet page has further resources including book recommendations.