Shopping over the Internet is obviously different compared to going to your local shopping centre; you don't actually get the chance to see the item you desire within reach, nor touch or try on.  But that doesn't mean you can't shop on Ebay.  The key word to shopping here is research.  Just say you wanted to purchase a mobile phone overseas, sounds risky yeah?  It isn't too risky if you do the proper research.

You need to make sure you know all that there is to know about the phone you wish to buy, for instance specifications, features and the extra items that are commonly included with the package, ie. charger, handsfree, phone strap.  When searching through the ebay sellers who are selling this phone, it is important to closely read the description they list for it.  Make sure what you have expected in the package for the mobile phone is what they are offering.  Once you are happy with a seller's item, it is good to check their feedback, for instance check to see if they are a power seller, or have great positive or negative feedback.  If they do have negative feedback, compare it with how much positive feedback, and also see what the negative feedback is for.  If it has been provided in regards to a mobile phone, you may need to continue doing further research.  It is also a good idea, to check to see if the seller has sold the same phone to other buyers, and if they have, check the feedback listed for them.  If you are happy with all this, the final thing to check would be price.  Don't automatically go for the cheapest price, check for the postage and handling fee, as well as any fee for insurance, if offered.  If you find this to all be reasonable, you can buy your phone!  Also leave an email for the seller to know that you have paid for your item, and ask that they email you when they receive the money and/or have sent the item.  At least that way you can get an idea of how long it would take to reach you. 
Happy shopping!