Answer 1

The only "LEGIT" way to get Ralts in Pokemon Black is through Dream World in Spooky Manor after 10,000 DW Points or by trading someone who has Pokemon White for it.(Ralts is found in White Forest in Pokemon White(EXCLUSIVE) but for Black, Dream World or Trade.)

Comments

I have Pokemon White want me to trade you a Ralts just tell me your FC and I'll tell you mine and I'll go catch one real quick and trade it too you for basically anything..(I Don't really care for trading I might get a hacked Pokemon but just to breed it and have a legit one myself lol.)

Answer 2

You have to trade. Ralts can not be found in the wild in Black. In white it can be found in white forest but in black it is not available.