What to wear during winter in Dublin?

Hey all, I (F) am coming to Ireland almost when winter is about to start, plannig a lot of outdoor activities and don't want the weather to stop me but being African I have no idea what nor how to wear for winter and what essentials to buy. Any advice? I am planning to buy everything when I arrive to Dublin. What did you find actually useful to enjoy outdoors - how do you layer - what to wear to sleep is ut cold in houses.