The 'best' food depends on him.
What may be the best match for one dog, may not be the best match for yours.
I would start by doing some research with this site:
Dog Food Review Ratings
It will link you to information regarding commerical foods, home cooking, raw feeding and supplements.
Also, there is a sticky at the top of the Health and Diet section that has the contact information for some of the more recommended (YT recommended anyway) brands. Many of them will send you samples or coupons if you contact them and request them.
Do some trial and error runs with your little one and see which food(s) seem to be the best match. It will be evident when you have found a keeper from the results you see. Most importantly, when you try something new with him, do it gradually instead of all at once.
Good luck and welcome to YT.