My first pistols were a CZ 75 SP-01, and a GSG 1911-22, in that order. A large part of your decision should be based on what your goals are.
Blow off some steam, put holes in a target, leave with a big grin? Go to your local range and try out a bunch of pistols in 9mm. I shot a lot of them before I settled on the CZ SP-01 and the Springfield XD. The reason I bought the CZ over the Springfield? Availability. Most shooters agree the CZ's are great pistols. They may look like a Volvo to some, but they're dependable and shoot anything. A lot of shooters I know hate the Springfield XD cause of the trigger pull. Personally? I love it, and would happily shoot it all day. The thing with these two pistols, is that they minimized
my faults when shooting at a target. I could pick them up, put 3" groups on a target at 7m and leave happy. Focus on 9mm cause it's dirt cheap.
Become a more accurate shooter? Again, go to your local range and try out a bunch of pistols. Find something that's comfortable, that you like, and then supplement it with a .22LR. Don't listen to these guys who says .22 is boring. Of the people I shoot with, the ones who care about being a better shot, have a .22. You remove a lot of variables with a .22 so that you can focus on steady sights, grip, and a steady trigger press. Once you have that down pat, those skills will translate to any other pistol. If I start getting trigger happy with my 9mm, and start spraying my shots, I calm myself down with the .22. It's called getting back to fundamentals. Guess what? Pro athletes return to fundamentals all the time.
Those who say .22 is boring are probably saying that because they're not finding a way to challenge themselves. I shot a Steel Challenge last weekend with my 1911-22 and had a ton of fun with it. In my squad, there were 3 other guys shooting .22LR. They all had fun. Two of those guys also shot 9mm in the Steel Challenge. Why did they pay the extra money to shoot .22 in addition to their 9mm's? Cause they find .22 fun. I'm not saying that you're going to find .22 shooting fun. I'm saying, it's cheap, it's a good way to work on fundamentals, and you should find out for yourself if you like it.
Also, there's the fact that after you put 100 rounds of .22 down range, your 9mm will feel like a cannon
