What kind of dumbbells should i use to when i start lifting?

At age 50: no more than 40 pounds! My opinion only Hope it helps Dr Z

Whatever's handy: Whatever weight seems right to you, so that you can work up to three sets of ten rips with good form and then increase the weight. Same advice you'd give a sixteen year old. No reason not to be as tough as everybody else just because you're fifty years old. Glad you're doing this. Good form is key -- you can hurt your joints a bit easier at your age but it's better than not lifting at all.