whats the best method in farming exotics? crucible or doing some strikes?
There is no farming exotics.
The only place you can get an exotic straightaway without being purchased is a reward in the post-game of the crucible or a strike. Randomly.
You can get an exotic out of a legendary engram which you can find anywhere, anytime in the game: patrol, story, raid, crucible reward.
You can get a legendary engram from the reward of a really difficult strike, or you could get a legendary engram from killing the first shank you see in the cosmodrome.
It's random.
The only thing you can do is play the game and hope one comes along.
I've done hours and hours and hours of farming and have gotten absolutely nothing for it. All of my purples and exotics I've gotten randomly from playing in various areas (crucible reward exotic, legendary engram for killing a dreg on the moon after a public event, killing a goblin on venus, etc).
It's random.