Ghiradelli Square and Dragon's Gate is quite a distance from each other - you could possibly walk it, but it's a 30-40min walk with a lot of steep inclines along the way (depending which route you take), so probably not the best option. Having said that though, walking will allow you to fit in a visit to Lombard St along the way and will take you through the back of Chinatown and you will end up at the Dragon's Gate entrance (eventually). San Francisco being the birthplace of Uber, I would probably suggest utilizing this option as it's only a 10min ride and will only set you back $5-$15 depending on what ride option you select. Failing that, you could always just catch a cab if you don't know how to (or want to) use Uber. The other option would be to catch the trolley car from Ghiradelli Square and get off somewhere on Washington St and walk the rest of the way to Chinatown.

It is the Bush Street and Grant Street