This post may be a bit controversial to some, but what I am about to tell you is the truth. Put those light dumbbells away and start lifting heavy. If you are serious about toning up your body then heavy weights will give you what you seek.
Doing loads of reps will not elicit the muscle growth needed to make your arms or whatever body part you are working on look toned.
I know that a lot of ladies are afraid to lift heavy because they think they will end looking like man. This is just ludicrous as you do not have the male hormones in adequate quantities to look like a man (and I am not talking about female bodybuilders) .You will instead look like a fit, toned and strong female capable of performing daily tasks with ease. Instead of endless reps with a 3kg dumbbell for example try lifting some heavy compound exercises such as deadlifts, squats, rows etc.
Take a look at female Olympic lifers are they full of muscle? Nope, they just look fit and are in excellent shape.
I don’t want to hear the other comment: I am too old. You are never to old start lifting. Lifting weights that are heavier will build muscle and bone density which is important as you age as the risk of osteoporosis increases due to lower levels of oestrogen. The loss of muscle which is called sarcopenia can also be stopped and reversed by the correct amount of training provided your diet and life style also change.