Gusto expresses positive feelings; use it to show that someone appreciates an activity very much. He watched the fireworks with gusto.
Pro Tip 2/3
Informal Setting
Best used in informal situations, 'gusto' might be too casual for formal writings or speeches. They joined the party and danced with gusto.
Pro Tip 3/3
Active Involvement
'Gusto' implies active participation in what one is doing, not just a passive interest. She always listens to lectures with gusto, asking questions and taking notes.