I am lady, mid- 30s and am lifting 8lbs weights doing simple exercises found on Pinterest. I'd like to get lean, beautiful muscles.

So far, I do 4 reps, 2 sets.

What is best number of sets to accomplish this? Is 2 ok, or should it be 3 sets?

Also I have 10lbs weights and I am thinking to use 8lbs on first set and 10lbs on second set.

How is this overall approach?

UPDATE
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Trying to build strong muscle, endurance, while loosing flab, especially the abs.