I would say that you have already set a good base up. if you already have 223 ammo on hand then that is a good caliber to go with to develop your shooting skills as the low recoil will make it easier to avoid developing a flinch. I would recommend a weatherby vanguard in 223 with a cheap Redield or Nikon 3-9x scope. you really need to develop your skills close and work out to range gradually. your best thing to focus on now is to get good at ranges within 300 yards and then work out.
you can worry about more powerful long range guns once your skills have been honed.
all guns lost in a tragic smelting accident.
I never said half the crap people said I did-Albert Einstein
You can't believe everything you read on the internet-Benjamin Franklin
Bean counters told me I couldn't fire a man for being in a wheelchair, did it anyway. Ramps are expensive.-Cave Johnson.