In my experience, the ticket prices for Ryanair to a particular place is usually at its lowest when you book it 4-6 weeks prior to the flight date. Sometimes it may be 6-8 weeks. Naturally you will also have to account for seasonal trends like the tulips season in Amsterdam, where cheap tickets are usually booked months in advance. Also, booking via debit card saves you the credit card fee, but it usually only costs a few cents. Try not to buy your return trip so quickly. Instead, watch both the to and return ticket and buy them separately. This way, you can squeeze every euro from Ryanair.
Once your tickets are settled, there is something called online check in. This happens 15 days to 2 hours before the flight. You simply have to go to the Ryanair website and click online check in that is at the left side of the site. The earlier you check in, the more front your seat will be. Also, if you are travelling with your friends, so check in at the same time or risk getting different seats.
Because your Eurotrip frequently involves air travel, plan your bags wisely. iPads and laptops need to be taken out during the baggage check, as well as your boots. Do it in such a way that you can take off what you need for the clearance in the fastest way possible. No point taking out your iPad that is squashed beneath your load of clothes in a panicky manner. What I do is that I have a backpack and a camera bag. Passport and ticket is in my camera bag that I sling to the front, and I put my iPad in my beanie and hold it on my left hand. Easy off, easy on. Also, after you pass the security clearance, you are normally out of water, and none of the airports that I have been to so far has a water cooler past the checkpoint. Either buy it from the cafe inside or stick to tap water from the toilet.
Most importantly, make sure that your bag fits the 55x40x20 carry on size limit. The guy actually measures your bag if he feels that it is too big. And if it is really too big, he slaps a 50 euro fee on your face. Not a pleasant experience and I have seen it happen to many people.
Normally, boarding early is a good idea because you can settle into the plane as soon as possible. For Ryanair, that may be a bad idea. Early boarding means that you have to stand in the line outside the airport to wait for the plane to be ready, and it can be really cold. This is because their planes are like taxis. One flight alights, 10 minutes later, another flight boards. If your seat is like rows 1-10, take the front staircase, if its from 21-30, take the back. If you are in the centre, it doesn't really matter.
Also, bring your own puke bag if you need. Ryanair doesn't provide one. And remember to allocate about 1 hour to check in. For us, we have to check in at the baggage check in counter before we head to the security clearance point. Sometimes there can be a lot of people and the queue moves slowly, so 1 hour is a comfortable buffer. If time gets too tight, just cut the queue and say sorry and point to your departure time. That worked for me. To a pleasant trip!