I've been down this road online and it's difficult to get Irish records since they are not immediately available to view - you have to order the image. And to order the image it means you have have to spend money ordering something that may or may not pertain to your relative. It's a guessing game sometimes. I found it to be a better use of my time and money to hire a genealogist to do the initial searching for me. That way, when I finally showed up at PRONI for a day of research, I had some information to go on.
They are super helpful at PRONI, but I'm glad I did some info gathering ahead of time as it made the experience much more fruitful.
The 1901 and 1911 census are available and I accessed them through Ancestry.com. For earlier records, it's helpful to have someone there who knows how to access information.