[Reiver]

For an inexperienced firearm owner I'd recommend a revolver because it is double action and takes a deliberate move to send a round down range.
Do not purchase a Glock or similar non safety /trigger safety semi auto...experienced folks have common accidental discharges with them and you are not experienced.
I've been teaching firearms safety/shooting to new comers for years.
A 9mm has a lot of penetration capability (may go thru a home wall into the next room) and that is a consideration for home defense and a semi auto takes much more training to use properly/safely.
I'd suggest a 38 special revolver or a .357 magnum that you can shoot .38's from until you get the confidence and ability to handle the .357.
The .357 magnum has the highest one shot one kill ratio of any firearm in the US today (coroner reports).
Remember this.....training. Practice on a range is nothing like acting in extremis and you will do what you've practiced good and bad in that situation.
If you do arm yourself for home defense then practice at home (dry runs)...where is the firearm, who does what...if we are separated what is the safe word (so I don't shoot you in the dark)...where do we go to make a stand, who dials 911, have different safe places and postures.
This may sound silly to you but 9 out of 10 home owners/gun owners never do this....as if it is second nature to them or something.
Do what the military does, have a plan, practice it, be proficient.