Credit Score Management

I need to build my credit again and plotting on getting a secured credit card. My credit score now is 550 so i want to raise it up to 700+. Just curious as to how long will it take to build my score up again? How much points does a person gain in a month? Thanks.

I have cleaned up my credit and my score is 661 right now. Should I wait until it gets over 700 before applying for a mortgage? Is there anything else I can do (besides paying bills on time) to get my credit score up a small higher?