There are over a dozen of ammo types for 9mm that are readily available for purchase.
Most common are 100ish, 115ish, 120ish, 120ish +P/NATO, and 147 subsonic both in FMJ and JHP variants.
You have tradeoffs between recoil, penetration, and bullet velocity.
115 and smaller are either target rounds or for small pistols to reduce recoil. I'd probably load a 9mm subcompact with lighter rounds.
147 is a heavier subsonic round that is claimed to have stopping power for defense and is used by some LE agencies.
124-126 is somewhere in the middle, and the +P is a overpressure variant which is a very powerful load--which in a JHP arguably can make the best defense ammo. It also can wear out pistol components quickly.
Buy a box of each, take them to the range, and see what you like. Most people will target shoot 115, because it's cheap and has very minimal recoil. Most larger guns with stiff recoil springs won't cycle 100 grain reliably.