If you want to get this achievement fast, but not pass up on any achievements (savior, for instance), there is still a way. After rescuing your fourth little sister ( in siren alley if you have been rescuing all of them), you get your first gift from the little sisters. Inside is some ADAM, money, and the gene tonic Proud Parent. KEEP THIS ON AT ALL TIMES! It will net you 40 more ADAM per little sister (120 from gathers instead of 80). This will help you out very much in the long run, especially with the Demanding Father tonic that speeds up harvests by 2x.