Why does the Torah add the word "ve'Chol Terumah"?
Rashbam: It comes to incorporate the Terumah Gedolah and T'rumas Ma'aser that the Levi separates. 1
It is the Kohen who must go to the granary to receive Terumah; so why does the Torah write "ve'Chol Terumah asher Yakrivu la'Kohen"?
Rashi (citing R. Yishmael in the Sifri) and Seforno: The Pasuk is referring (not to Terumah Gedolah, but) to Bikurim, which is also called 'Terumah', and which one brings to the Beis Hamikdash. 1
Rashi: As the Torah writes in Mishpatim, 23:19. And the Torah here teaches us that one gives it to the Kohen (Sifri).
What does this Pasuk teach us?
Rashi, Ramban and Seforno 1 : Refer to 5:9:2:1*. It also teaches us that, as opposed to Terumah, 2 Bikurim must be brought to the Beis-Hamikdash 3 and given to the Kohanim of the Mishmar that is currently serving in the Beis-Hamikdash (Ramban and Seforno).
Ramban #1: It teaches us that, once one gives the Kohen Terumah Gedolah, it belongs to him, and whoever steals it from him must bring an Asham Gezeilos. 4
Ramban #3 (citing the Sifri): Seeing as the Torah does not give a Shi'ur for Terumah, the Torah is teaching us here that whatever one designates as Terumah takes effect and must be given to the Kohen
The Ramban however, explains the question differently. According to him, what R. Yishmael asks is that the Pasuk cannot be referring to Terumah, since the term "Yakrivu" is used exclusively in connection with something that is brought on the Mizbe'ach (See Ramban, DH 've'Od Shanu', who elaborates).
Seforno: In the way that one brings the first-fruits to the Owner of the land