Having done it extensively over the last few years I'd recommend;
1. West Cork. Pretty much anywhere in West Cork. The road out to sheeps head is a good one, albeit a single track, windy, grass growing in the middle kind of road.
2. The ring of Kerry. All of it. Stopping for pancakes in Strawberry Fields (on the road past Barphinny lake at Molls Gap). Making sure to take in the Gap of Dunloe, Connor Pass and Valentia Island.
3. Donegal coast including a stop up at Malin head.
West Cork & Kerry are my favorites.