What's the best way to build wealth? Invest in a diverse selection of quality companies and hold on to them for the long term -- ideally, about 20 players or more for at least a decade. Over time, they could deliver top returns and set you on the path to financial freedom.But don't worry: You don't have to rush out and buy 20 stocks all at once. You can pick up a few here and there and gradually add to your portfolio according to your budget. Investing is a lifetime pursuit, so you have plenty of time to bu ...