First you have to get a Target gift card at a discount. Giftcardzen is sold out though. I think they had them at 6% off though.
If you did you could get a $100 Sears gift card and still have $15 on your Ebay gift card for $84.60.
Right now it's really hard to get a target GC at a discount because people have been going crazy buying them to get in on this deal. Also, people have been having problems getting the ebay GC from target using a GC, lots of cancelations reported. Lots of people also complaining about it taking a long time to get their Target GC. If you also don't shop at target much, you'll most likely have left over balance, which isn't the easiest thing to spend.
10% off ebay GC is already pretty good, if you have a target red card, it's almost 15% off the ebay GC, cause the 5% red card discount stacks. I've bought several hundred $$ of the ebay gift cards using my red card and it came almost instantly.
By all means, if you want to buy a target GC to buy an ebay GC to buy a Sear's GC, more power to you, but it's not a requirement and somewhat of a pain given the run of target GC's. Just my opinion though, it's your money!