I didn't think to travel until I was in my 40s, so our idea of traveling is just being thorough in shopping for room rates and rental cars. We always spend three weeks to amortize the airfare better. Now that I'm in my 70s, I'm still careful with costs, but more from habit than need.
Traveling off season is probably the best way to get a good airfare. Having flown IcelandAir in the past, I'm deluged with "Dublin for $329" emails. Make sure you include them in your searches. Last minute tickets are sometimes a deal if you can be spontaneous.
Hostels are now priced where hotel/B&B rooms were just a few years ago, so camping might be another approach. Carrying all your gear in a backpack or bicycle avoids the absurd car rental rates. Irish weather can be difficult for hiking/bicycling as you venture off-season.
We have a friend that travels completely foot loose. She arrives in a place and just rolls the dice on meeting people with a spare couch - AirB&B used to offer that, but they've evolved from that simple model.