Ive used just two sites for my tree
Scotland's people and genes reunited
i started about 8 years ago then i decided to get back into it 2 years ago currently have about 666 people on my tree most of my lines Ive traced back to the 1500-1600s the irish parts of the line are the hardest to trace mainly due to the costs with the offices that hold those records but i know most came over during the famine era
if you cant prove the person with paperwork or prove someone Else's data then avoid adding the information into your tree its worth using a back up tree for refining and adding to rather than screw up the main tree your working on