Baral's Expertise

If you cast a card "without paying its mana cost," you can't choose to cast it for any alternative costs, such as emerge costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Cathartic Reunion, you must pay those to cast the card.

The card that you cast may be an artifact or creature that was returned to your hand by this spell.

While you're casting your free spell, the Expertise spell is still on the stack. It will be put into its owner's graveyard after the free spell is cast. The free spell can't target the Expertise card in your graveyard. It can target the Expertise spell on the stack, but the Expertise spell will become an illegal target before the free spell resolves.

Effects that allow you to "cast" a card don't allow you to play a land card.

Any triggered abilities that trigger while performing the Expertise spell's first effect won't be put onto the stack until after you're done casting your free spell. They're put onto the stack at the same time as any abilities that triggered while casting that spell regardless of the order in which those abilities triggered.