I like Bullseye for loading the .45 ACP -- others will disagree.
If you have a Dillon 550B, you will probably best be served with Dillon dies.
For brass, I use range pickup, mixed brass. I have accumulated about 10,000 pieces over the years. You can look in the ammo section of Shotgun News and find once-fired brass advertised. If you want new brass, I like Starline.
I shoot mostly cast bullets in .45 ACP, and like the Lee 230 grain tumble lube cast out of straight wheel weights and lubed with liquid Alox. this is a bit smoky in an indoor range, and requires cleaning both pistol and dies every so often, but it shoots well.