Flogging a dead horse?

The title is pretty much what I have been thinking about my website for the last 2 months. Ever since I got the 'unnatural links' email from G, the website's ranking went down in the toilet. I have tried a number of things and felt very demoralized when nothing worked. Was depressed for the last week or so trying to justify whether the website was worth 'fixing'. Thanks to the guys on this forum, I was able to make the hard decision of rebranding the website and launching under a new domain. It goes live in a day and I feel relieved at making a decision to change my circumstances instead of crying the 'why me' song over and over. My question to you guys is whether I should do a redirect from the main page of the old site or just put a big clickable banner on there saying the site has moved?

Flogging a dead horse is now over now you are on the right track

big clickable banner on there saying the site has moved?

Would be my way forward