One of the crucial strategies to win this game are the fire dragons: Play three huntresses in a row (or wait for two, if your opponent made the mistake of already having played one) and get the fire dragons... they accumulate quickly as they're the easiest way to get gold, but the fire dragons are often worth 3 or 4 points each. So with 5 fire dragons, you could have 16 points which usually puts the game in your favor

Secondly, I'd say the tip with dwarves, never play one on an empty place wait for your opponent to make that first move, or wait till you have 4 dwarves

Let your opponent spill one of his 4 sorceresses on the first black dragon, and have another black dragon + sorceress combo ready to play afterwards.

Ships can be important when the cards accumulate enormously, but they will usually gain you much less compared to the tips above, keep in mind however that there are only 6 ships and use this knowledge to your advantage

But, again, fire dragons are the key to victory!

Also, it's important to count the ships both players have played. It's huge benefit to start stage 3 if your opponent has only 2 ships left in his deck. Then you can decide to keep playing until almost all cards have been played and then collect huge points from ships.