1) The Poskim are divided on this issue. The Sefer Hilchos Maaser Kesofim says in the name of Rav Shmuel Felder shlita ( A respected Posek in Lakewood, NJ) that he heard from Rav Shlomo Zalmen Auerbach Zatzal, and YB"LCT,from Harav Yosef Shalom Elyashiv Shlita that it is prohibited under all circumstances.
Other Poskim maintain that as long as there is no limit to the amount of tickets being sold for the item, you may use Maaser money to purchase the tickets. This is the opinion of Rav Moshe Feinstein Zatzal (Igros Moshe Orach Chaim Vol. 4 Siman 76)
According to this if there are a limited amount of tickets being sold in the auction/raffle, then Maaser may not be used for their purchase.
Some Poskim allow maaser to be used in all instances, even when a limited amount of tickets are being sold. (Rav Shmuel Wosner Shlita in Shu"t Shevet Halevi Vol. 9 Siman 200. See also Shu"t Teshuvos V'Hanhagos from Rav Moshe Sternbuch Shlita Vol. 3 Siman 289)
There are so many other opinions in this, with different conditions and stipulations, that it is impossible to write them all here. As always, for a final Psak please consult your Rav.
2) Some Poskim maintain that if you win, indeed you should give the amount of the ticket purchase to Maaser again. (Rav Moshe feinstein ibid.)
3) Rav Moshe also maintains that you must give Maaser on what you won, as it is no different from any other income you earn. He writes that it is proper to give this Maaser to the organization from whom you won the prize.
4) Once you put the money in the Pushka, it belongs to the Tzedaka/Organization, and you may not use it for any purpose from which you will benefit. If while you give the money to the Pushka, you stipulate that you are amassing this money for their auction or rafle, perhaps it would be OK. As with everything, consult your Rav for a ruling.
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