In 9mm, start with a used CZ 75 or Sig 226. All metal so soak up a bit of recoil, are DA/SA and if you don't like DA you don't have to use it, and buying used will not depreciate much if at all. Parts and magazines are easy to come by, the guns themselves are easy to work on, and both need very little maintenance or special care to function well. They also both have a .22 conversion if that is a draw for you. There are always people looking to buy these guns, so if you don't like it you can sell it at near no loss. Once you start going to the range trade trigger time with guys around you, and you'll find preferences.