seriously, don't go into that much detail in embryology, you'll end up taking a long walk into the mersey

i think its one of those topics that you either love or loathe. just know the martini atlas stuff - have a good idea about the process of the first week or two development i.e blastocyste and implantation etc (can't remember much about it tbh, so i may be making words up) then look at each layer ecto, meso, endo and look generally at what happens during development and which layer develops what.
dangerfield seems to like foetal blood circulation so know the differences between the foetal heart and umbilical vessels etc, and why they are like that. and then the process of how the foramen ovale closes during birth - something to do with different pressures on different vessels or something, i really cant remember and cant be arsed to look it up right now
and finally, look at the role of the placenta, what can cross it, what can't, structure etc.
i only used martini with the atlas and that did me fine, but go with what you're happy with.
tbh, once you get your head round the wierd little lizardy thing that we all started out as and figure out which bits going to turn into what you're kinda there.
hth xx