Further to Flexibles added notation, and Admins comparison to real golf, can Admin tell us when we can swap and change a ball at any time in practice mode please?
This game has limitations as it is a computerised golf simulation, so comparisons are futile.
But for the OP - you must have rocks in your head buying such an expensive sleeve of balls at your level, skillset and the clubs you have.
Yes balls wear out and will be lost of you find a hazard or OB, so start by using balls that cost les than 100cr for a sleeve. With your equipment I would not buy any balls.
Equipment (and ball) upgrades will improve your scoring, but as you know, you can play this game without spending a penny. If you do decide to upgrade - ask the forum for advice as it will save you wasted credits on poor purchases. Also many players never actually open their own wallet, by doing surveys etc they can upgrade at a cost of only their time.
Just bear in mind, WGT is a business, not a charity, and whilst you can play for free you have limitations and a disadvantage against players with better equipment.