Feedback is really important but when you are new at selling, buyers take that into consideration. I sold my first site for $500 dollars... Of course I did not have any feedback at that time, but it still sold for a good amount.
On that auction I made sure I added the following:
"I Want You To Bid With Security And Confidence!!!
I am new at selling websites on Flippa, so I am adding the option to purchase using Flippa's Escrow Service. Of course you can still purchase using PayPal if you will like. I don't have any feedback, but hopefully that will change soon. I am always online, so if you have any questions or comments then please ask and I will reply.
Please, Payment is due within 24hours of the end of auction
Thank You!!!"
The buyer wanted to pay with PayPal, so that was good, but what I am pretty much trying to say is that... You might want to just work on selling websites and getting feedback from people the regular way. It might seem like it will take forever but it really won't. Also, make sure you ask them to give you feedback, and give them feedback as well.
I start my websites out at $30 dollars so if I sale the site with only 1 bid of $30 dollars then I will at least make a very small profit lol. Most of my sites sell for more than $30 so that is good, but you just have to find your range... The feedback will come so you don't have to worry about that. Just keep working hard, and it will pay off.