Well, I'll take a crack at this....

I would say the best place online for beginners to learn about Donne is Anniina Jokinen's Luminarium site.  She collects publically available essays about Donne and his poetry (as well as a good deal of other Donne stuff).  The link is

luminarium.org/sevenlit/donne/donnessays.htm [not donneessays.htm]

She also gives the necessary caviats about dealing with online scholarship.  The quality of these essays varies quite a bit (some are by very respected scholars, others by students).  But it sounds like for your purposes--personal curiosity and pleasure--her webpages about Donne might be a good place to start.