The really useful things I would do are:
Join a gun club so you can get more practice.
Mag well funnel, I like the Smith & Alexander which may require gunsmithing depending on how good you are with tools.
Lose the plastic mag catch, and replace it with a good metal one, I used an Ed Brown extented catch and it was a drop in part that actually dropped in.
A good trigger job is a must, mine is running around 2.5lbs.
Checkering the front strap is a good modification, but skate board tape is a cheap substitute that works great.
Borrow someones else's gun to try out a flat(or arched) mainspring housing to see which one fits your hand better. I have small hands, and I find that the flat mainspring housing works best for me.
Ambi safties are nice, but I haven't really used mine much. Extended safties are great, and I thinks yours already has one.
Get a good progressive reloading set up, like a dillon 550b, you'll need a lot of ammo.
As many hi-cap mags with extended baseplates as you can afford. I find 4 is minimum, but I get by on six. I'm using the Arrendondo base plates now, but if I were to do it over, I would get the Dawson pads because they are easier to take apart.
Get a couple of different weight recoil springs to see which works best with your gun/load. Then buy extras of which ever weight you settle on.
Don't buy any titianium parts, they're a waste of money.
I don't know anyone who still pins thier grip safties. There are so many different styles available now you'll be able to find one that will work for you if this is a problem.
If you find that you still have money left, let me know, I'll think up some more ways for you to spend it.