What is the meaning of "Kohanei Hashem"?
Rashi: The Nesi'im (princes) of Hashem.
Radak, Malbim: Foreigners will do your work, so you will be free to serve Hashem, like Kohanim were prepared and designated for Avodas ha'Mikdash 1 . So you will be free from all worldly engagements, and engage in Toras Elokim and Chachmah, to know Hashem.
Malbim: Yisrael supplied Kohanim's needs via 24 Matanos Kehunah. So Yisrael will serve Hashem, and Nochrim will supply their needs and tend their flocks and land.
Why does it add "Mesharesei Elokeinu"?
Malbim: Kohen is from the seed of Aharon; he is proper for Avodas ha'Mikdash. Only one who [exclusively] serves Hashem is called Meshares Hashem, but not one who engages in secular needs.
What is "Cheil Goyim"?
Rashi citing Targum Yonasan: The property of star-worshippers.
Radak: Aside from serving you in your 1 land, they will bring to you gifts of gold and silver and all the good of their land.
Radak citing Ibn Ezra: The relation of Nochrim to Yisrael will be like Yisrael to Kohanim (refer to 61:6:1:2 and the note there). Cheil Goyim corresponds to Ma'aser 2 .
We fixed the text of Radak to say 'Artzechem' (PF).
We give Ma'aser to Leviyim, who help the Kohanim. It is reasonable that if no one helps the Kohanim, Kohanim receive Ma'aser. One opinion says that Ezra enacted to give Ma'aser Rishon to Kohanim, because no Levi proper for Shirah ascended with him. (PF)
What is the meaning of "uvi'Chvodam Tisyamaru"?
Rashi: You will be in place of them, to have the honor that they took until now.
Radak: You will be elevated and aggrandize via their Kavod, i.e. their money. The Yud is in place of an Aleph; this is like "va'Shem He'emirecha ha'Yom" (Devarim 26:18).
Radak citing Targum Yonasan: You will delight.
Malbim: All of them will honor you.
