Here are places you can find Rare Candies and Master Balls.
1. In the pokemon mansion when you battle all the maids in the correct amount of turns you`ll battle a rich lady or gentleman. Use theif on their blissy and you'll get a rare candie. Blissey might use fling so be careful.
2. In snowpoint city, right from the Pokemon gym, in an empty square space.
3. Behind the pokemart in the fight area or survival I forget.
1. Migrate a pokemon holding a master ball from leaf green/firered/ruby/saphir e/emerald
2. Trade with someone.
3. At Jubilife city go to the lottery thing. if you match everything you'll get a master ball you can try again if you save, change the time to 23:59 (Not the date or then you cant do this for 2 days)then walk around till the poketch watch says 00:00 then you'll be able to take another ticket.