If you currently have no rifles, and this will be the one and only, at least for a while, I'd recommend the 30/06.
You'll be able to find ammo anywhere ammo is sold..you'll have a greater variety to pick form wherever ammo is sold, it'll be cheaper than all other ammo you've mentioned (maybe the same as ther 270) ..... and you could pick up brass at any range ...
Then you can move up and down the power range for the purchase of any other rifles.
Just my opinion....
And I think you'll find more left handed offerings in the 30/06, but I might be wrong on that.