IMO the best course of action is...
1. Suck it up and buy some of the factory stuff to store and have on hand. Shoot some to zero your rifle and save the brass.
2. Scrounge all available brass and load your own
3. Watch for "deals". They don't exist anymore like they used to. A $29 battle pack of SA surplus now goes for $65. I made a little money on mine but I'm now to the point where I am keeping the rest because it CAN'T be replaced.
As for places to order from, Midway, AIM Surplus, Cheaper than dirt, and sportsmans guide have all been good to me but I don't know who has what. IIRC, AIM has lithiuanian stuff and Winchester but neither is really that cheap. Sportsmans guide has Winchester FMJ too but it is slightly more expensive there than it is at AIM.
I am taking my .308 out tomorrow to zero it.
My ammo?
40 rounds of handloads using Winchester 760, 150 grain Speer BTSP's, and scrounged (meaning FREE !) Cavim and LC military brass. Total cost for this ammo is about $14.66 for the whole 40 rounds. That is $7.33 for 20 rounds of ammo loaded with decent JSP ammunition as opposed to twice that for FMJ. And it is about twice as accurate as the surplus I used to shoot - no complaints about that. But even with reloading, ammo isn't exactly cheap anymore.
Before you buy a .308 I'd suggest you buy a 10/22 first if economics is your primary consideration.