Some players really hate the grinding. I'm not sure if it's the xp-side or the credits side, but if it's the time it takes to get the credits, and yes, you can also ad your boosters. But it's still limited how much extra the booster can give you. It doesn't work like, you enter the battle, going afk for a couple of minutes, and then you've earned the biggest profit. You have to do something on the battlefield yourself.
The booster can only help you SOME of the way, as they mostly only lasts for 2 hours each of them. But once they've ran out, and you still have credits to earn and grind, what do you do then?
One way to get more credits, is to load more AP than gold shots, and invest time in learning about weakspots. It takes time yes. But if you know where to hit, your target you don't have to use premium shots. A Cromwell can still with regular Armor Piercing/Armor Penetrating shots, penetrate the armor of for example a Fury. If the cromwell player, knows where to aim. If your opponent is angled, or hull down, then either go for other targets, or other spots on the current target.
It is in the end up to you. But I haven't had a single battle in my memory, where I've used "gold-shots" and ended with a profit. -Not even with a premium acc, in a premium vehicle.
Am I full of shit? A tomato? Ok. Don't take my words for it. Go try yourself.