Ping/latency depends on many factors, the main ones being physical distance, congestion on the line between you and the host, and type of internet connection.
Speed tests from speedtest.net pick the closest server to you by default, and usually measure speed between you and that one location that is close to you physically, often with a major ISP within your city. Ping/latency tests on the other hand may chose a location that is a bit more distant from you, so you will get a different result. In fact, pings can be very different depending on time of day, current congestion on all nodes between you and the destination, physical distance, peering arrangements between your ISP and the backbones that route to your destination, etc.
As to your question, yes, your connection lag seems normal, it is sufficient if you are not experiencing any noticeable delays. 50ms ping is not noticeable and most games are designed to allow some lag. 50ms is 1/20th of a second round-trip between you and that location. That said, your ping will vary depending on who you are connecting to, their physical location, type of connection, etc.