Personally, I disagree with everyone who says that you will be better if you pay for crowns and premium tokens. True, auto scouting and trading is very useful, but let's be honest, you can gain that gold with trading in half an hour, if you know how of course. I had only one premium and it was when I started playing, didn't even knew what I was doing at first place, but as the time passed, the game became very interesting. Farmville more complicated? lol, you don't know how to play SHK then ;)
I got better because I was actually playing it, completing quests and communicating with other players in the world.
And yes, this is actually multiplayer game and yes, you can actually be attacked by other players. What do you know, it's multiplayer game, real time strategy game, it's not like in single player game, you save it and continue from there. This game has a very complexed mechanics to understand, so if you are not willing to think a bit what to do, then play candy crush saga.
Cards - those are helpful and I got those from completing quests, not buying them. And I don't use them at all, I just stockpile them just in case if needed.
Highly recommended to play.