What are "Ma'asai"?
Koheles Rabah (2:8): They are the Luchos - "veha'Luchos Ma'ase Elokim Hemah" (Shemos 32:16). 1
Rav Sadya Gaon: My wealth. Ibn Ezra - this is like "Asah 2 Es Kol ha'Kavod ha'Zeh" (Bereishis 31:1).
Ibn Ezra: My great deeds.
When did he aggrandize his deeds?
Rashi: In the days of his grandeur.
How did he aggrandize his deeds?
R. Avigdor: They were greater than my ancestors' deeds, e.g. "va'Ya'as ha'Melech Kisei Shen" (Melachim I, 10:18).
Seforno: In order to draw my heart from investigation to striving for needs of temporary life, I increased deeds proper for a king, more than other kings normally do - "Banisi? Natati? Asisi? Kanisi? Kanasti? Asisi" (4-8).
Metzudas David: He did great, wondrous deeds, like the verses tell.
What is the significance of building houses?
Rashi (10, citing Koheles Rabah 2:8): This refers to Batei Kenesiyos and Batei Midrashos.
Rav Sadya Gaon: They were castles.
R. Avigdor citing Koheles Rabah: He built the Beis ha'Mikdash, and his own house.
Metzudas David: He built many houses [and planted many vineyards].
What is the significance of vineyards?
Koheles Rabah 2:8: This refers to rows of Chachamim, who sit like rows of a vineyard. Kerem b'Yavneh was not a vineyard! Rather, they sat in rows, like in a vineyard.