Reloading... The cost varies according to what equipment you use.
For 120 rounds a month, the classic Lee Loader would do. It costs around twenty something bucks. They have them on Ebay, Amazon, etc.. A plastic-faced hammer, or a cheap arbor press from Harbor Freight is required.
Most 223 loads use 25 or so grains of powder, there are 1000 grains in a one pound can that costs around 35 bucks.
Primers are not very expensive.
For a good bullet that can be had cheap, look at Midway for the Hornady 55 grn FMJ BT bullets. - I buy them in bulk to save more.
Brass you already have, but in a pinch, you can usually find once-fired brass at the range, laying around.
With more expensive equipment you can do more, of course. - I have had very good results though in the past, using a Lee Loader.
Lee makes a hand-held press that uses regular reloading dies. At around 50 bucks, it is the cheapest press on the market, but it still does a very good job.
I use a bench-mounted RCBS press that came in a kit with a powder scale and several other tools. - It all cost me 250 bucks or so, several years ago.
If I had to do it again, I would use Lee products only. They make a great bench-mounted press. The Lee case trimmer is inexpensive and easy to use. I have used several brands of dies and like the Lee dies best.
- But that's just me. - I think you get the best stuff for the money from Lee.
Best loads on the web are at powder company web-sites. I use the Hodgedon web site a lot, and the Ramshot/Accurate Arms site too.
Buying a reloading manual or two is best, but there again is another wad of cash to spend. I would recommend buying one manual at least, as they contain detailed info about reloading that will explain the hows and whys of everything.
My preference if I had just one would be the Hornady manual, because I tend to use their bullets most often.