I searched best practiceis and such but could not find this answer, When I do a project I normall choose by country. For the most part I choose between 4-8 search engines to use as I dont want to always post to the same sites it scrapes. Normally I can get anywhere from 100-400 verified links this way.
Am I short changing myself by doing it this way? How many should be used on average AND can the same ones be used for each and every project even if running at the same time?