Hi DJ, welcome to the forum, glad to see you have escaped from the GB forums.
The first piece of advice would be to get the motorhomeparkingireland app which for about a fiver is very useful. Contains locations of sites, aires, wild camp stops, and many pubs that allow overnighting. There is a campsite guide called the green guide which is probably better than the tourist board one.
This site is very friendly and useful, but my best advice would be to ask more location specific questions once you have an outline plan.
If you arrive into Belfast, then the obvious route would be round the North coast towards Derry and then into Donegal which has almost unlimited stopover potential. This also puts you firmly on the Wild Atlantic Way which follows the coast right down the west and south coasts.
The river Shannon can be followed from the Lough Erne waters in Fermanagh and then the whole way to Limerick. This gives a good feel for inland Ireland.
As you well know time will be the deciding factor. Search this site when you have a few destinations in mind and you will find lots of threads to base planning in detail on.
Davy