Like I said earlier...the main concept is weight progression. If u really wanna get serious , couple of 15-25lbs dumbbells won't get u ripped, sadly. Core exercises like heavy squats, bench, deadlifts are what form the basis of muscle and body composition.

However, at 15 yrs old, dumbbells will definitely teach u the underlying foundation of body building.....correct posture and most importantly, DEDICATION to the routine. I wish I had started my training at 15 yrs rather than at 35. It doesn't matter how much u lift..what matters is weight progression and making your ass stick to the same consistent routine at least 3 times/week ....to months..to years.