Putting the cart before the horse again...Don't even have a press yet but I want to squirrel away some components

Is there somewhere I can get all the powder, primers, brass, bullets reasonably?

Resized bullets or not? Is there just a die for this?

How much powder would need and which types of bullets (AP, API, etc.) should I focus on?

www.patsreloading.com/patsrel/prices.htm

Here's what I recently ordered from Pats:

1000 pulled and sized ball projectiles
32 pounds of powder (I chose WC860 surplus)
1000 Hirtenberger primers
200 once-fired brass

I also threw in a can of about 700 sized API projectiles, since it was so cheap (~$80 plus hazmat).

Total cost with shipping and hazmat fees to Texas was $903.

I chose sized bullets since the price isn't that much different.  You can do it yourself with a sizing die that fits on most reloading presses.

Focus on ball ammo, if you want to shoot it.  If a range allows .50's, it will almost certainly allow ball ammo.  They may allow AP ammo.  Most places will not allow you to shoot API or tracer because of the fire risk.  If you want to save it for SHTF or the coming Zombie invasion, then API, blue tip I, or spotter tracer is good.

8 pounds of powder will do about 250 rounds.