When I first started shooting handguns: 4 years ago now (The day I turned 21 to be exact) I started out with just some basic Silenco ear muffs.
I soon found out that shooting indoors is very loud, at first I found myself flinching as I walked into the range and other people were shooting.
I recommend you combine a "regular" set of ear muffs, along with the ear plugs that you squish between your fingers and insert them in the ear canal. (I now use Peltor TacSport Muffs still with the ear plugs and the volume turned all the way up on the Peltors.)
Some people like to get really nice shooting glasses, example oakley makes a cool set of glasses; however at a hundred dollars a pair for glasses that your going to scratch (and you will scratch them) I would opt for a pair of Cabela's brand Shooting Glasses, or Peltor shooting glasses. (Anything that meets ANSI Z87.1)
As for a range bag, I used any bag that could contain my gear, I have went through several as the stitching of most bags seems a little meager for all the weight I tug along. I now use the Uncle Mike's Deluxe Range Bag and its holding up so far. I have a regular fishing tackle box for my tools (screw drivers, punch set, pliers) and accessories like snap caps, cleaning solvents and all the little nick knacks.
I recommend the Otis Tactical Cleaning Kit, I know you only have 1 .45 but I really like this kit as it included several brushes for different calibers and is a great alternative to the old rod cleaning kits. I also like to use Hoppes No.9 solvent and Hoppes Dri Lube.
Ammunition is still the cheapest at Wal-Mart. Usually Winchester White Box (WWB) Value Packs are the best deal. Right now the pickings are a little meager and local shops tend to charge you way to much. There are some good deals to be had online. Places like:
Ammoman.com
sportsmansguide.com
ammunitiontogo.com/
ableammo.com
OR You can go to:
http://gun-deals.com/ammo to find user submitted data of the most current ammunition offerings with price.
budsgunshop.com has great prices on handguns and accessories.
If your looking into hollow point home defense ammunition, it costs a lot more: and you should fire a few hundred rounds just to make sure its reliable in your handgun. I know sometimes this is cost prohibitive since hi grade ammunition cost a hell of a lot more than range practice ammunition; still you always need to make sure that the ammunition you are using is reliable in your gun.
Its for you to decide how many magazines you want to buy. Some people have a hell of a lot because they only like to reload once.
In my case I have 5 for my HK, 2 for my 1911, and 4 speed loaders for my revolver. I suggest factory magazines, just purchase as many as your willing to afford, as they can be expensive. Its going to be rare in a self defense situation that your going to need more than 2 magazines.
You can have all the "gear" in the world, however if you dont practice its not going to mean squat.
Practice, Practice, Practice, then Practice some more, then after that, practice, Practice, practice, then more practice, then more practice and keep going and going and going
I know traditional training is the best: but there are some great videos on youtube. Here is one of them:
http://www.youtube.com/watch?v=0v-mxvnFLfc
So what it comes down to:
Basic Handgun Safety & Knowledge
Bore Brush, Brass Jag .45, Solvent, Lube, Patches: To clean your firearm
Hearing Protection: Since your shooting indoors I suggest Muffs combined with ear plugs
Eye Protection: Anything that meets: ANSI Z87.1
Ammunition: (I never trust someone elses reloads: sorry fellas)
Range Time: LOTS OF RANGE TIME!!!!!