Dave,
As this is your first trip, I'd also highly recommend pre-reading Europe Through The Back Door as it will provide a lot of important information for planning your trip. Pay special attention to the "Rail Skills" chapter.
Due to flight times and time zone changes, you'll arrive in Europe the day AFTER you depart, and the last day will be spent on the trip home. Be sure to factor that into your planning.
One other important point is to allow for adequate travel times between cities. Your travel times will include checking out of the Hotel, getting to transportation, the actual trip and then getting to your new Hotel and checking in. That all takes time. For example:
Dublin to London - at least half a day, even by budget air
London to Paris - again about half a day. Depending on where you're staying in London, you'll have to get to St. Pancras station. You'll arrive in Paris at Gare du Nord, so it will take some time to get from there to whichever area you're staying.
Paris to Munich - that trip will be about 6H:09M by TGV and other fast trains (depending on which train you select).
Munich to Prague - that trip will be about 5H:06M (again, depending on which train you select).
As someone else mentioned, it's a bit late to be booking accommodations for Oktoberfest. You may have to stay in a nearby community, perhaps Augsburg.
I assume you're using open-jaw flights, inbound Dublin and outbound Prague?
Good luck with your planning!