@Bendy Nguyen I recommend reading all of them at some point since Shakespeare's work is so influential to this day (and there's a lot of great content to analyze and learn from), but a good starting point would be the more popular ones like Sonnet 18, Sonnet 116, and Sonnet 130.
These are what first come to mind for me when I think about a classic sonnet (even if Sonnet 130 is more of a commentary than your typical love poem). If you have already read them since they are so popular then I recommend my current favorites which are 119, 90, and 28 since they are very enjoyable to read (in my experience).
@Adam Gary My personal favorites at the moment are Sonnet 119, Sonnet 90, and Sonnet 28. 119 has some of my favorite imagery in there, 90 just has so much emotion that I keep coming back to it, and 28 is something I like to read when I'm either too tired/can't fall asleep since I find it fitting.