$200 in cash or Target GCs. I use that to buy an eBay GC on Target .com for 5% off. I never tie up more than that.
For one thing, it's rare to be able to purchase more than one of the Target GC deals on ebay at any time. Of course, if you have multiple eBay identities, that number would be multiplied. But I like to keep things simple and easy to follow. And I don't count on being able to get the 4X eBay Bucks offer, so I don't purchase the full-price Target GCs that also tack on a shipping fee.
Once you have that Target GC, then you can purchase another eBay GC to use when the Target GCs go on sale again. Doing this churn over and over again until I need to purchase my Disney GCs.
I have the advantage of time on my side. I have enough Disney GCs to pay for my DVC dues for this year. I just need to add to my stash for my 2017 dues and to pay for any food or experiences that I want to reserve for my 2016 trip.