I would say in order:
1. Good instruction
2. The discipline to dry-fire every day. One can replicate everything for firing an accurate shot except recoil and fast follow up shots. I set up scenarios and run through them using my carry gear.
3. For real-life tactics and techniques that work and finding your own reactionary gap for drawing and firing accurately - SIMUNITIONS with a live, thinking (and trying to shoot you!) partner. Noting beats this type of training - although Simunition rounds and the conversion kits are not cheap.
4. Dillon reloading equipment. Can't beat it for consistency, cost and accuracy, and the Dillon "No B.S." garuantee can't be beat.
5. Active competion shooting. Especially IDPA, IPSC and Bowling pins.
Stay Safe.