The Hide never ceases to amaze me, in a good way. I'm glad that we've been able to get beyond "The salmon is 13 years old" stuff and give him decent answers to his questions.
Here are my thoughts, salmon. If I had to choose between a 6.5CM and a 308 assuming the same barrel length for an all-around rifle (say 22-24"), then the 6.5CM is going to give you better ballistics. However, for a kid (not a pejorative term here) just getting into LR shooting, you've got to prioritize what you HAVE to have versus what you WANT to have. In that sense, I think a 308 is a better buy for you in terms of ammo availability. If you were going to be making your own ammo and could spend a couple grand on the components to always have 6.5CM on hand, then I'd say go for it. But you're going to be competing with a lot of guys to get the factory Hornady 6.5CM ammo whenever it becomes available, whereas 308 ammo is more available in general. Practice practice practice. There's a saying that crops up a lot on the Hide: the Indian is more important than the bow and arrow. Give a bad shooter a fantastic gun and the shooter's bad form, habits, etc. cannot take advantage of his rig. A great shooter on a factory 308 will outshoot the bad shooter with a TacOps every time.
For someone just getting started, the rifle that will give you the most trigger time will be the best one for you. Even though a lot of guys shoot the big boomers (myself included), many of us have .22LR trainers so that we don't have to spend thousands of dollars to maintain the fundamentals. Beyond 22LR, a 223 match chamber bolt gun will give you great, inexpensive practice in learning to read wind and judge distance (and therefore bullet drop).
So get a good rifle, a good scope, and save your money for ammunition since you probably won't be reloading for a while (unless you've got a parent/relative/close family friend that will teach you). Once you have the equipment, you need to learn the fundamentals that make you a good shooter, which means finding someone who can mentor and teach you. You don't want to practice bad habits. Be patient, and take this one step at a time. I've been shooting since I was your age and made many mistakes (and wasted a good chunk of money), simply because I was self-taught. Some guys who are self-taught are winning matches and masterful shooters. That tends to be the exception, and not the rule. If I were you, I'd definitely get a training subscription to Lowlight's videos and watch them (and re-watch them). Practice at home with dry-firing (and practice VERY safe gun handling practices!!!), then when your parents can take you to a range, practice perfecting a few of Lowlight's techniques at a time.
Good luck, and keep us informed with how you're doing.