I want to make sure I understand the game's currencies and am a bit confused:
1. When I play PVP I earn diamonds and blue skulls - what are blue skulls for and how do you use them? I see I can spend diamonds for base upgrades. is that it?
2. When I play campaign missions I earn cash and "XP". What is XP and how do you spend or use this?
3. My main question is about cash and gold. I find it's easy to earn cash - it builds up quickly when you play campaign missions. I see the Store however only takes gold. How does one earn gold? From what I gather I earn 5 pieces of gold when I complete a level and I can earn a piece of gold when I watch a video. Otherwise, how does one earn it? I see you can buy it from the app store, is that the only way!? I find I'm often gold deficient and yet have surplusses of cash? How does one spend the cash if not in the store?
I know these questions are basic and that responding might take someone a few minutes but I would appreciate it. I've searched online and can't find a faq or answers to these.