I came upon this via a FB ad. Haven't used it before. Much of what I need is transcribed not images on here but still saving a ton of stuff to sift thru later. Which great migration are you talking- Scots or Irish?
I am on Ancestry.com Have relatives in Scotland and that is somewhat helpful but to have full access to Scottish stuff- Scotlands People is better source but VERY costly. I 'met a few people on Ancestry who have access looked things up for me. If you are just starting I would recommend going to your local library and using Ancestry on there. The Library edition lets you look at a bunch of things that you can't look at on the free version at home. You can email the images or information to yourself and then save to a file.
Not as enamored with the new Ancestry. I use FamilyTreeMaker program on my laptop- the functionality is way better than the online thing. You can merge things you find, keep lists, write yourself notes on each person and it is waaaay easier to navigate than the online thing. Also not keen on all the personal info floating in the online cloud. Not too expensive and well worth it. I would get that, populate as much as you can on your tree then hit the other sites. Most of the sites will have trial periods but I would use those only after you exhaust the library versions because they cover a lot and are free.
I have the international version of Ancestry. If you ever need me to look up someone let me know.