Having a gun fitted is not all that expensive BUT, before it is really worthwhile you need to have a consistent gun mount. Best way to do that is to shoot a lot.
Except, if the mount is incorrect to start with, practicing and ingraining a bad habit is harder to unlearn. Better to learn proper form and mount before shooting a lot - as in get a lesson or three from a reputable coach. Then get the stock fitted, and THEN go shoot a lot - practicing your mount and proper form with a gun that fits.