The first is Final Fantasy Adventure. It is... also called the early version of The Legend of Mana.
Final Fantasy Adventure, Secret of Mana, Sword of Mana (never released outside Japan), and Legend of Mana are called Seiken Densetsu 1-4 in Japan. Fact.

Besides, there are other FF spinoffs out there. Tactics, Tactics Advance, and Crystal Chronicles come to mind.