What did he offer on the Mizbe'ach?
Radak: Olos and Zevachim (Shelamim).
Malbim: The [70] Parim that are offered for Olos in the Mikdash.
Why does it say "ba'Chodesh ha'Shemini ha'Chodesh Asher Bada mi'Libo"?
Rashi: He expounded that this is the month of Asif (gathering Peros into the house); the Chag should be in this month. "Bada mi'Libo" is an expression of falsehood; he concocted. Radak, Tosfos (Menachos 52b) - this is like "mi'Libcha Atah Vodam" (Nechemyah 6:8). Chazal (Menachos 52b) said 'he is Bodeh (takes out) Se'or from them and ferments them.
Radak citing Targum Yonasan: He fixed it according to his desire.
Why is mi'Libo written like Milvad?
Radak: It is Milvad (in addition to) Mo'adei Hashem. We do not find that he did so for other Mo'adim like he did for Sukos. Perhaps it was the beginning of his kingship, like I explained above (verse 27), therefore it says that this Chag he made up from his heart, and the same applies to the others. Chazal (Yerushalmi Avodah Zarah 1:1) said that he concocted also Shabbosos and Yamim Tovim.
What did he burn on the Mizbe'ach?
Radak: Olos and Zevachim (Shelamim).
Malbim: The Ketores; he made himself like a Kohen Gadol, who enters on Yom Kipur to burn Ketores. Kohanei ha'Bamos offered the Olos.
