There's no real secret to getting this, my method was to save every Little Sister, and I never bought Plasmids (you get plenty as a thank you for saving the Sisters), instead I focused on my health, EVE, and slots. Doing this I maxed out one track before I faced Ryan. Just focus on which track and it should come quick.
Note that you must advance the story to enable the purchase of further track slots, so you can save ADAM or upgrade other areas without worrying about running out of ADAM.