No experience with Ryanair specifically, but airlines do oversell their flights. That said, if you check in as soon as you are able, right at 24 hours before, you should be ok. The people who run into trouble are the ones who wait to check in until they get to the airport.
Pulling up to a light that was changing from yellow to red, when a crappy blue hatchback zoomed past me and the car in front of me in the next lane over, through the just-turned-red light. Local cop was first in line at the cross street and pulled out with the lights going. Saw the guy pulled over about a quarter mile down the road. Waved cheerfully.