How James 2 Relates to Genuine Faith

Questions about whether 1 Corinthians 3:15 indicates that a person can be saved but have nothing to show for it in the way they live, and whether a lack of good works after salvation means the person is not really saved.  

• Does 1 Corinthians 3:15 indicate that a person can be saved but have nothing to show for it in the way they live, and if so, how does this fit with passages like James 2 and John 15?
• If good works demonstrate/follow salvation, does that mean I’m not saved since I still fail so much when it comes to selfishness, not helping others much, not giving much, etc.?