Did Ryanair invite you to try again? If so, I would suggest doing a JOC in a 737 sim immediately before the retake. I think both CTC and OAA offer them and they won't have any pre-requisites other than an fATPL and a couple of grand. Given the number of OAA grads going to RYR, that might be a good place to prepare via a JOC if RYR invited you to try again.