The dative case for adjectives is identical to the nominative case, so they don't change; however, in Ulster Irish the adjective will be lenited in the dative singular with both masculine and feminine nouns when the article is present (I believe in such cases some Munster dialects eclipse the adjective):
Feminine noun
U: chuig an phictiúrlann/phictiúrlainn bheag
C/M: chuig an bpictiúrlann/bpictiúrlainn bheag
(M: chuig an bpictiúrlann/bpictiúrlainn mbeag)
Masculine noun
U: chuig an ghort bheag
C/M: chuig an ngort beag
(M: chuig an ngort mbeag)
There's no change in the dative plural (in some dialects there is a dative plural ending -ibh which is added to nouns and sometimes adjectives, you may come across this in reading, but don't worry about using it).
In compound nouns, only the head noun is inflected, the rest of the construction doesn't change.