I am 16 and my parents just bought me a dumbbell set from 5 to 40, now the best I can do is 25 and I can do that with about 8 reps(I know i am skinny). Is it good just to stick with dumbbells and do diff workouts with it. So like after I can do 25 easily, I should move to 30 and then 35 then 40. Does that sound good?