The believer is saved by faith alone, but not by a faith that is 'alone'. Faith without works is dead (James 2). Still, no one can be justified before God by works of the law, or, 'doing good' (Romans 4; Galatians 2). Faith in Christ saves. A belief that faith plus works saves is heretical and leads to eternal damnation. Why? Because such a belief says that what Christ did for our salvation is not enough. We must add to it.
If you have a faith that does not do good you have an illegitimate faith. If you have a faith that needs works to complete it you have an illegitimate faith. If you have a faith that looks to Christ alone for justification you have correct faith.
If you have a faith that does not do good you have an illegitimate faith. If you have a faith that needs works to complete it you have an illegitimate faith. If you have a faith that looks to Christ alone for justification you have correct faith.