The most glaring omission that I see is the need for a laser rangefinder. Once distance gets out past a couple hundred yards, it becomes increasingly difficult to guesstimate range correctly. A GOOD QUALITY laser rangefinder is a must, not an option.
Second would be a reliable wind meter
Next....find the most accurate load for your rifle and practice practice practice AT LONG RANGE. Sitting at the same ole 100 yrd bench and shooting the same ole targets will get you nowhere fast. It's better than no practice at all, but it's not going to teach you how much distance changes everything. It also won't teach you things like the effects of torquing the rifle (gripping too hard, pulling the rifle or pushing the rifle), cheeking the rifle too hard, etc...Long range practice will humble you like never before when it comes to your form.
Once you get decently proficient at moderate to long ranges, make a dope chart. A dope chart is an index card that you use to record what your bullet impact is at different ranges and in different wind velocities. This is where you'll do your first serious exercises with your new wind meter. Most seem to use a 10mph wind speed as a reference, since it's a pretty common wind speed for "normal" atmospheric conditions.
Then..........you guessed it.......practice some more. A lot more. Before long your friends will be talking behind your back about how your a liar. Things like "there's no way he shot that deer at 700 yards. It was probably more like 70, hahaha." That's when you know your getting there.....hehehe.]
There's a WHOLE LOT MORE to being confident at long range than what I just posted, but that should get you thinking in the right mindset. Next, read as much on forums like this one as you can and learn from some of the incredible marksmen here.