Since you're collecting to Scott pages, use the Scott catalog. With Gibbons at least, you will be constantly translating numbers. You can buy original pages for Ireland only, cut out of the relevant Scott volume, from a seller on eBay
. I think it's "chirokmd" or similar.
But another way to answer this is, from whom and where will you be buying stamps? If from US dealers, most use Scott and a handful use Gibbons. If you're buying in the UK within the country or from an eBay
seller there, they'll use Gibbons. If you're going to STAMPA in Dublin or buying from MacDonnell in Ireland then use that catalog.
My advice as a long time collector of Ireland is, if you're in the US, start with Scott; if you're into specialty material like control markings or plate markings then get MDW; and you have extra budget throw in Gibbons.