Actually the consonants are much the same, but the vowels differ quite a lot. The other Gaelic language is Manx which has a spelling system based on English. As a result the spelling is totally unrelated to the grammatical structure. This is a bit difficult to deal with. I generally read it aloud and try to translate it into Irish as the sound of the languages is very similar.
Irish vowels are very easy.
They are only single sounds, not diphthongs like English vowels. They come in two varieties, long and short. Irish does the same thing in a very systematic way. Each consonant is pronounced either in a broad or slender way, according to the surrounding vowels. Irish has fewer consonants than English.