Taking a class or lessons is a great idea. Especially one where they have rifles and gear to loan you and you can see what works best for you.
For some time, the go to for long range was 6.5 Man Bun but it does not have to be that way. Really, any rifle where you can manage recoil and get consistent results is the one. However, that changes for some.
Depends on the job, really. If you just want to ring steel or punch a hole in paper, which are valid pursuits and lots of fun and full of hair-pulling challenges, you don't need a big and heavy bullet.
If you are hunting game of assorted sizes at differing distances, I would think nothing less than 7 Rem Mag or 7 mm PRC. Someone I know hunts Aoudad with a .300 Win Mag.
Someone else hunts everything with a .300 PRC and other with .300 WSM.
That's why the suggestion to take a class can really help. Even if you build a medium priced rig, you will start with more knowledge to say, okay, that action and barrel are good. That trigger is good. That scope looks good to my eye (a very subjective thing that should not be overlooked.)
My amateur opinion and pick is 7 PRC for feral hog up to elk. Though, hog hunting, I would be better off using my Windham Weaponry R16SFST-308 (AR-10.)
I have a few other .308 W rifles and really anything 400 yards and under is going to be fine with that. In fact, for hunting, which is my primary activity, I go by impact velocity rather than energy. So, average 2700 - 2800 fps MV in .308 is good to about 300 yards. And that is fine for the heavily wooded south where I live and the southeast.
In the western part of my state is desert and there is a state drawn hunt for mule deer and they say in the description to be able to shoot to at least 200 yards. Turns out that mule deer cannot be harvested by putting salt on their tails.
I think with kestrel in your id, you are probably settled on some ideas and just looking for confirmation? Happens to the best of us.