Powder and Primers: Powder Valley is definitely a good place to mail order Primer and Powder. You have to weigh the shipping and HazMat fee against your local store prices (including sales tax).
I have one store in town whose powder price is about the same, but primers is 20% higher. So if I just need powder I buy locally. If I need primer I get about 10,000 and the powder and that spreads the hazmat fee, so the price per 1,000 is well worth it.
Sometimes the big named retailers (MidwayUSA, MidSouth, CTD, etc) have a sale on primers that makes it worthwhile, but the stars have to align (their sale, my need, and my funds).
Bullets: I've pretty much settled on two suppliers for most of my pistol bullets.
For lead bullets and for jacketed .357, I buy from Magnus (
http://magnusbullets.com/) though they can't keep up with production of the jacketed so you have to give them a long lead time (4-6weeks).
An alternative to lead bullets is copper plated. Loads the same as lead, doesn't cost much more. As long as velocities are under 1,200fps they work great. I get .45, 9mm and .44s at Berrys (
http://www.berrysmfg.com/).
Both companies use USPS Flat Rate, so up to around #50's ships for about $11.
Brass: No reason to buy 9mm or .38spl, unless you're a purist. Plenty of stuff on the ground at a range. Even .45ACP and .40SW isn't hard to find. When I go shooting, and I'm feeling needy, I ask everyone on the range (7 bays) if I can have their brass. Just come get me and I'll sweep your lane for you. Only other reloaders say no. You do need to be careful with 9mm and sort our the ones with swollen bases. These are typically IPSC/USPSA shooter making max PF with 9mm. Not a big price to pay for free brass.
But for all my brass purchases (.357 and .44) I've settled on Starline (
http://starlinebrass.com/). You can buy it direct as well. Everything I've bought from them has been first rate. They're endorse by a number of the pro shooters, including Golob, Tequila, Koenig, Jarrett and Platt.
Tumblers/Vibrators: People are all over the map on this topic. I only clean really really dirty cases. I use a vibrator with walnut shell medium. I use to deprime and then clean so there was some chance of cleaning the primer pocket, but typically the pockets just clogged with medium. So now I clean before I deprime. I've never tumbled completed ammo. The bullet itself shouldn't be "dirty" and if the case is that dirty then I do it before reloading.
Casting: I've moved away from lead for pistols and gone to copper plated. Much cleaner and much safer medically, especially if you shoot a lot indoors. I've never felt the need to cast. Some like to do it and some don't.
Hope all that is a help, others will I'm sure chime in with other resources and opinions.