How many reps and sets to tone my arms?

It all depends on what exercise you are doing, e.g. lateral raises, curls, over heard presses, etc.

The 3 sets of 15 reps sounds ok but you should be using a weight that you can only do 15 reps with and not more than 16.

If you can do 16 reps then use a heavier weight. Bodybuilding and toning is usually done with 12-15 reps.

Bulking up, use 8-12 reps and heavier weight and strength work do 2-6 reps at your RM.

RM equals “Repetitions to the Max”. These are normal or average guidelines but every individual responds differently to the number of reps and sets and amount of weight used.

If you just want some toning do about 15 reps and 3 sets,

yeah uve started with 5lb do 3 sets of 15 3-4 times a week but do your triceps as well or else they’ll grow slower! When uve noticed after a while there not growing say after a month get a higher weight of dumbells and 4-5 sets of 12 reps! good luck peace!

p.s do your chest and shoulders first so that your bicep/triceps dont give up on you throughout your reps! And you have 2 major muscles in your biceps so try working them in different angles- concentration curl, dumbbell curl, DB hammer curl, wrist extention are good for targetting them both! you have 3 major muscles in your triceps and the bench dip is the best and also- single arm extention, lying DB extention and twisting kick back.

GOOD LUCK