With my grandparents both in their 90s, I started researching my family tree, much of it Glasgow based. Scotland kept centralised records from 1855 onwards so it's been fairly simple until you go beyond that. Scotland's People has been an excellent resource.
The Famine forced most of my ancestors from Ireland to Glasgow, and I've arrived at a dead end as going backwards, I lose them in Ireland. Does Ireland have centralised records? I know NI has them databased but does the Republic?
A lot of Irish records were destroyed by fire but you might find something using the links on this site http://www.findmypast.ie/irish-census-records. Some parishes may have baptismal, wedding and burial records available.