Welcome to the Forum. We're pleased that you dropped by. Congratulations on your new A550.
Several suggestions: The Sigma 17-70mm or the Sigma 18-125mm if you want a little more zoom. Since the A550 has IS built into the camera body, you want the older non OS versions of these lenses. www.KEH.com
recently had a used Sigma 18-125mm non OS lens in the Sony mount for around $150.00. KEH is a very highly respected e-tailer.