I have 1 pirate now given to me after I finished a quest in the game. Now my question is: Do I have to buy the second and third or even the fourth pirate for 18.000 crystals each or is the game giving me the other pirates during the game play after finishing other quests? What do I have to do to get another pirate? I want to build juggernaut and spacewanderer ships.

dont dream about another free pirate in quests :/
that's the only one you get for free,althought you might get a "black label" in expedition (not sure what are your chances for that,but it's VERY LOW) a black label adds +1 lvl to pirate,...getting 2 black labels from expeditions is just like winning lottery irl...yeah ,there is who did it (you can count them by your hand probably :p ) BUT..not with some low expedition level.

conclusion : no;there is no more free pirate levels in quests--for jaggs and space wanderers,those are made for the players ready to spend on game--or just play long looonng lonnnng enough till you get 2 black labels (getting just one is much of luck itself)

18 000 Hydarian crystal ! are this game is made for presidents?

I guess 2 Black LVL getting is a dream, percentage, 0.00000000000000000000001

And what about jouann? Pirate LVL 5? 

Thank you all for the answers. So this game is only for russian multi millionaires I guess. :)