Its okay to have more than one or two credit cards but there are certain stipulations to making them work to your benefit.
If you've had trouble with debt before because you've lacked some level of spending discipline then hold off on trying this a bit until that is addressed. If you're ok in the disciple department or you keep an ultra low balance on your one credit card then know it will not hurt your credit if you have another. Once you have it your biggest job is to make sure you do not ever keep a high balance on either one.
It shows you can manage a large sum available to you without going crazy. If this happens and you keep everything else with your money in order, you should see some improvements in your credit score.