Hobby search and amazon.jp/amazon us for me. I have points saved. Ebay you can get good stuff it you read the description and ratings. The buyfag guide is your friend.
Buyfag guide. Just don't buy from china. Even though all japanese figures are made there the ones they sell on ebay are casted from the original molds but with shitty materials and paint.
The guide has everything you ever need to know.
Also my figure collection site is a good way of asking question/showing off/ they have a person to person selling forum. They have ratings. Trust others who bought from them.
List of bad ebay sellers
http://myfigurecollection.net/club/139/discussions/&did=3636