So 300 grain is super light. 500 grains is a good goal with a 10-15% FOC. If you use a single bevel you need to know the orientation which I believe most come factory right wing.
I shoot 550-600 grains with a cutthroat broadhead (toughest I’ve tried and I’ve hit a lot of rocks, not one broken) and I have 200 grains in the tip with FOC around 17%. These arrows are also for Alaska hunts and elk though, my buddies all shoot around 500 grains and FOC around 11 or 12%. Whitetail are easy to kill if you hit the vitals, weak bones.
Now for the bow I haven’t used it but there’s great deals on Ebay and craigslist. I’d go Mathews, bought a newer Mathews chill X for under $400 and it doesn’t get any better than a Mathews! Shop around a bit and get a good one, used they’re quite cheap and even the older ones are great.
Most important is get a bow, take it to a pro shop and get it tuned to you, get some shooting lessons, and paper tune with your final set up! Tunes cost like $20 and save a huge migraine and the lessons shave months off your learning curve.