Man,you gotta stop changing your mind and just get a rifle and shoot it. Get a Savage 10FP or a Remington 700 SPS and get a $200-ish scope and shoot it. Total package under 800 bucks.
You admit you're a beginner...learn your marksmanship and get to be a good shot before you upgrade all your gear. You don't need a sniper stock or top-of-the-line optics,it won't help you...yet. When you improve you will notice the difference that those things can make. Kinda like how novice shooters get a custom 1911 when a basic Kimber or Springfield would do just fine.
In fact (my opinion only,worth exactly what you paid and no refunds given) I would use a .22 to learn with. If you can't get a decent group with a .22 what makes you think you can hold a decent group at 600 yards with a .308?