I think a shotgun is a good choice, if you are only going to have one firearm, because of it's flexibility. A good friend has and really likes his Mossberg, although I think he has the 500. I doubt there is a much of a difference in how it works.

The other shotgun you might consider that is similar is the Remington 870. It's probably the most popular shotgun ever made. So, lots of them are around and lots of parts for them are around. And it simply works. When it is cold and wet and not taken care of, it still seems to work. When it doesn't work, it's not tough to take down and fix. I bought a Remington 870 Wingmaster used for about $250.

If you are shooting skeet, it's tough to shoot the doubles with a pump. A double is when targets are launched from both houses, probably less than a second apart. You need to hit one, then shoot the other. With an autoloader, you pull the trigger once then twice. With a pump, you'd need to find time to pump in between. Your other option are just don't shoot the doubles, shoot the targets flying single for fun and enjoy or get an autoloader from the range when you want to try to shoot doubles. I've done both. My wife has an autoloader, but so far I have not shot her 20 gauge youth model.