In general terms, sticking to a primarily varied plant/fruit diet, with as little meat as you can tolerate is best for a lot of things, everything from gout, cholesterol, blood pressure, and the list goes on...
It is not a good idea to jump on 300mg of Allopurinol.
You need to start @ a much lower dose and build it up, and you should be monitoring your uric acid levels along the way.
This is not a drug to casually start taking without a doctor's supervision.