The best deal for me are the "Lucky" containers. Since I have so many tanks, I usually buy a TIer V container and normally end up with 7500 gold as compensation for a Tier X I already own. If you can buy a "Lucky V" container for 5 Euros, 7500 gold in return is a (relatively...) good deal. Nice video
I got the mystery box in the first attempt and got the mystery certificate from that mystery box. I got Concept 1B to open the mystery certificate. 0:43