What are optimal conditions to achieve gains strength training?

Many things: Optimal health conditions to gain strenght include a good work out routine that keeps challenging you (change it every six weeks), diet that is rich in protein and veggies, normal hormone levels because if you are low this will not work, ability to work out, as well as vitamins and amino acids.

Depends on stage: The good news is that if you are new to strength training, almost anything you do will lead to gains. The most important thing to do at first is to learn proper technique so that you set up a lifetime of good habits, and injury-free training. Two extremely effective three day a week beginner programs include starting strength and stronglifts. Both emphasize whole body compound exercises.