Re: Hiking gear/shoes required for Jinshanling
Regular sports shoes would do. Can be rainy in May too.
Those merino shirts are awesome but unless you have a subsequent need for them they are pretty expensive.
It's already in the low 20s C here in Beijing so I think by May you can safely expect it to be pretty hot. Bryan's right that it can get colder and windier, but as long as you have something to deal with that in your daypack, you'll probably find yourself hiking in a t-shirt most of the day. I always like to pack a fresh one to put on for the ride home so I'm not sweaty on the way back.
don't skimp on water, and don't forget a hat. They're the 2 most important things of all.