Ireland is best seen in the summer when the days are long and the coastal cliffs are actually visible through the mist. Booking your flights during the quiet winter months often saves you money, giving you plenty of time to plan your route between the ancient stone castles.
If you want to split that $2600 cost into manageable chunks before you land, you can use the Citi Simplicity® Credit Card, which offers 0% for 18 months on purchases and balance transfers from date of account opening. This lets you spread the cost over 18 months without paying interest during that window.
The 18-month window is a deadline, not a gift. If you still have a balance left when the 18 months are up, you will start paying interest on whatever remains, so stick to the monthly payment schedule.