II just want to tell people that, whenever you unlock a skin your chances of getting credits or a-coins don't increase, unless you unlock every skin of that rarity.

For example to explain suppose you have 4 rare skins remaining, and in 10 fortune vault the probability of each is 10% so total 40% chance to get a rare skin. If you get one rare skin, then the probability of getting credits or a-coins doesn't change, instead probability of getting the remaining 3 rare skins becomes 13.33% each which is again 40% chance of getting a rare skin. After you get all the remaining rare skins, then only your chances to get credits and a-coins increase  https://speedtest.vet/  .

So, to sum up, you should give priority to finish your 5 vault(rare skins) quickly to get much higher chance to get credits and a-coins at 10 vault. Also don't even try to spend resources on getting epic skins hoping to increase your chances of getting credits or a-coins. As you will end up increasing chances of getting epic skins only. And it's almost impossible to get all the hundreds of epic skins from 10 vault to increase your chances to get credits and a-coins.