Rachelle, from a lenders perspective I can tell you you're better off getting your credit and the rest of your financial house in order before you start to buy a home.
Your credit (score) is how a lender measures your willingness to repay your credit obligations. If you have a history of not paying them a lender is going to be reluctant to lend you hundreds of thousands of dollars.
As Sally said "not so great" can mean a lot of things, so get your credit and financial house in order first. You may be a first time home buyer but you won't make it to first time home owner unless a lender decides you are a good credit risk.