Are you trying to cross the pond too fast? Sometimes frustration with a “I don’t know where to reseach my German/English/Irish, etc.” ancestor is because the homework has not been completely done.
Have you looked at EVERYTHING in the area where your immigrant ancestor settled? Everything means everything, even things you think might not help. You never know what a document will say until you look at it. Clues can be in the most unexpected of sources sometimes.
Then research his or her children completely as they might have left clues as to their parents’ origins.
Don’t start your German/English/Ireland research the minute you learn your ancestor was German/English/Irish. Do your complete homework first.