There can never really be one best natural medicine, because you almost always need two treatments for gout.
The most important one is something to lower your uric acid levels. You also need to monitor those levels to make sure they fall low enough. If they do not fall below 6mg/dL, you are wasting your time. For most gout sufferers, there are few natural products strong enough to achieve a good enough reduction in uric acid. However, you may find that supplementing urate lowering drugs with natural products lets you take a smaller dosage. You must only do this after full consultation with your doctor (preferably a rheumatologist).
Medicines work differently for different people. You have to keep searching and testing until you find the one that suits you.
The second medicine that you need is an anti-inflammatory agent to reduce swelling and pain. Again, there are several, and the best way is to choose from different natural anti-inflammatories until you find one that is right for you. As with most natural treatments, you will often find that a combination of several different compounds is more effective that a single substance. Many foods have anti-inflammatory properties. I have started to analyze these, and you can see a small selection by clicking the anti-inflammatory categories on the right.
If I had to choose just one best natural medicine for gout, it would be water. Lack of it always gives me a gout attack. Plenty of it always helps my gout attacks subside quicker. For more information, see my water and gout page.