Welcome to GT.
While most of us who've been around handguns for a while would probably suggest starting with a lighter caliber, to keep recoil out of the equation while learning basic handguns safety, starting with a .45 is certainly do-able. Some of us have trained kids at single digit ages to shoot .45s.
Rembember to keep a firm grasp with both hands and keep your body weight forward into the gun as you're firing. Make sure you have good ear protection to prevent startling/flinching due to the sound of the gunshots. The 30-series Glocks are soft-kicking guns as .45s go.
Best suggestion: as a first-time handgun owner, the best investment is early training. It will save "reinventing the wheel" and will pay off many times over in ammo saved and bad habits prevented as you continue your journey to mastering the handgun.
Welcome to our world, and best of luck,