I agree with those who say that the Shield is not a gun to use to test your accuracy. Yes, some (not me) can shoot a 3" group at 25 yards, but honestly, the gun was made to defend yourself at self defense ranges of of 7-10 yards with a center of mass sized target. If you can do that, you are good to go.
You should get a full(er) sided pistol to hone your handgun skills. I would recommend a 1911, 38/357 DA Revolver or a mid to full size 9mm like a G17/19, M&P 9, Beretta 92, CZ-75. Why do I not recommend a 22LR pistol? No recoil will spoil you and you'll have to relearn everything all over again when you move up and develop a flinch. When I shoot my SW 22A, it feels like I am shooting a 10/22. I simply squeeze the trigger and I never have to reacquire the target because the gun does not move.
To give you an example, here are some test groups with a Shield 9 at 10 yards. Not spectacular, but I would be comfortable saying that this gun can be used to defend me.
The little groups on the left are from the SW22A-1 22LR offhand at the same range. Shooting this feels like using a staple gun. Pull the trigger, punch a hole, repeat.
The other challenge with a handgun is that I have to shoot regularly to keep my skills up. Once I shoot a rifle, picking it up again a year later is no big deal. With a handgun I can really tell if I've been out shooting at least once a week or if it has been a month since I last shot.
Good luck and welcome.