Dubfag here, like the others have said, Wicklow mountains is your best bet for scenery and such.
You may also want to take a trip to Kingscourt Co. Cavan, there's a forest there called Dun an Rí, definitely not as big as what you would find in the US but it's a very beautiful, peaceful and quiet spot to chill for the day. It's owned though so no camping unfortunately.
Also watch out for scumbags knacker drinking if you plan to stay out overnight
