Forget the paid tours and go yourself. Easy to get to on The Bus, Chinatown is a compact area with many markets that are fun to explore. Like others have said, it is best to go early. Many shops will open at 6am, but going around 9-9:30 gives you plenty of time to look around and hit a place for lunch around 11 before the local business crowd comes in. (Legends at the Chinese Cultural Center was recommended to us by a local vendor and it was great with few tourists.) everything is closed up by 2pm and it is not recommended at night.
Look for the lei shops. Absolutely beautiful traditional and fancy leis are hard to choose from, have a heavenly scent, and are reasonably priced.
When I first researched our vacation, I found a food tour of Chinatown for $105 per person. Looking closer, I realized we could do the same thing ourselves and save $200. Chinatown is easy to see and enjoy without somebody ripping you off.
A word of caution that there are homeless people camped out on the sidewalk along River Street. Nobody bothered us, but it is a little disconcerting.