The minigames in Romancing SaGa 3, I believe, are the best ones out there. There are 3 minigames, 2 of them are only available to Mikhail.
Thomas's Business Game- you'll need Thomas to start it, but don't need him to finish it.
Mikhail's Ruling Game- Mikhail must be your main character. This is his attempt to rule Loanne and is the most difficult and frustrating game out of all of them.
Mikhail's War Game- a subsection of Mikhail's ruling game. These are his campaigns against various foes. Personally, it's my favorite of his games. Harid also has the first 2 battles of Mikhail's war game during his introduction.
This is just a list of the various tactics you may get in Mikhail's Ruling Game.