I'm new here too so I'm not sure what escrow is. As far as amount, I usually want the credit to by xbox/ps4 games. With tax and prime discount, I need enough to cover about $53
An escrow is a middle man of sorts. Generally, an escrow is a very high ranked/trusted member in the bitcointalk community. He will make sure the deal you may have with someone else will be safe.
Here's how it works:
When you find a customer, you contact the escrow
1) You send your side (the money) to the escrow
2) The member you are buying from will send his item (amazon gc) to the escrow.
3) The escrow will send you the gift card, let you redeem it, make sure everything is okay.
4) Once you give the escrow the go-ahead call, he sends the money to the other side.
It basically helps lower scams.