For EU nationals, a visa is not required to come to Ireland. Remember to check the validity date of your passport / identity card, this document must be valid 3 months after the scheduled return date.
Remember to take your raincoat! Rain is not uncommon, although most of the time it is just heavy downpours of short duration. Take rather warm things for the evenings, but also light for the day if you plan a mission in summer. For winter, the weather is similar to France!
The sockets are not the same as in France, remember to take an adapter for an English socket! You can also easily find them at the departure or arrival airport.
Life is slightly more expensive in Ireland, compared to France. Count 5 to 10€ to go to the museum, and between 8 and 15€ for a dish at the restaurant for lunch. A bus ticket is also worth at least €2.15 in major cities such as Dublin.