Lifting weights doesn't mean you'll get huge muscles (but you can if you want to). By lifting small amounts of weight every other day, you can build stronger muscles. Lifting weights every day can burn out your muscles, so waiting a day in between can help your muscles rest.
This will result in better posture, stronger bones and joints, and a higher fitness level. You don't have to buy weights - you can use food cans or water bottles. These weigh approximately 1/2 a kilogram.