If you’re in category 1, 2, or 3, you won’t even need to step foot in Ireland. If you’re in category 4: “An Irish association through a great-grandparent (or a grandparent where that grandparent obtained citizenship through naturalisation) and where there is no, or negligible, reckonable residency would generally be deemed insufficient to warrant recommending the Minister exercise absolute discretion to waive the statutory conditions under Section 15 of the Irish Nationality and Citizenship Act 1956, as amended and would result in a refusal.”
In simple terms, there is no specific amount of time, but the physical presence cannot be deemed negligible. If you are on a work permit, we suggest at least half of the year. If you are under the Immigrant Investor visa, we suggest at least a few months each year.