Firstly is for making a first point or stressing importance of order. First can be used the same way or for telling the order of activities... First, I would like to go over some things that were said last time.... Hmm. I wonder if this is important. Firstly, I would like to go over some things that were said last time... Sounds like it might be important to me. We went to eat, we went to shop, but first we picked up rick. - That is not much of a point and it is bot important. It is just stressing an order of events.

firstly means, as the first point. example: I like you because firstly (first point) you are polite and secondly (second point) you are good natured.