Online service to obtain Irish documents?

Hello,
I am trying to find an online service to help me obtain the missing documents I need to apply for Irish citizenship. My mother and her parents and my fathers parents were all born in Ireland. I have my mothers birth/death certificate and my maternal grandparents death certificates but I don't know their birth dates so I can't apply to get their birth certificates. I also don't know their marriage date (grandparents) so I dont know how to apply for that either. I tried online but actually ended up with the wrong marriage certificate. Does anyone know of an online company that will be able to locate the documents for me so I don't waste money getting the wrong and useless documents? Thanks so much, Margaret

Let's back up - if your mother was an Irish citizen, born in Ireland, then you are already an Irish citizen. Don't you only need your birth certificate and her information? Then you can get a passport?

If your mother and your father were not born in Ireland, and only your grandparents were, then you have to go the route of the Foreign Births Registry, and for that you do need their information.

I thought I needed to register at the FBR first? I did not realize I could get an Irish passport first. When I went to the site to register the FBR it asked for parents info which I have and then it asked for grandparents info as well. If I can get an Irish passport with just my mothers information then I will go apply. I did see that if you have parents born in Ireland you are considered an Irish citizen. I guess I thought it would be more complicated than just supplying my mothers birth certificate etc. Thank you so much, I appreciate it! Margaret