Shipping cost is the most remarkable cost which you buy from overseas. So, you can check estimate cost before ordering items. Most of the Rakuten stores utilize Japan Post Office which transfers in a propitiate cost and you can check at International Post - Check rates and delivery days.
amazon.co.jp has their own shipping system "How to Ship Internationally" and is also reasonable.
Combine shipment would be more cost saving, so ask your friends if they have anything they want from Japan!
Help you to buy Anime stuff direct from Japan to obtain authentic, rare with saving money.