Powder is usually the cheapest part of reloading for handguns. The components breakdown like this:
9mm load - powder 1 cent, primer 2.4 cents, bullet 6.5 cents. $5.00 per box of 50.
223 load - powder 7 cents, primer 2.4 cents, bullet 15-22 cents. $12-15.50 per box of 50.
That doesn't count brass, because you are reusing it. You can use most non magnum pistol rounds for so long it might as well be forever (you will lose it before it breaks). You can load 223 3-5 usually. Common calibers are easy to scavenge. Or you can buy once fired brass fairly inexpensively on craigslist, at gun shows, on midwest gun trader etc.
55 grain ammo is fine for 1 in 7. You can probably shoot the heavier loads well, but 55 grains is where I would start my tests.