The second ability will count Gyome itself on the turn it enters the battlefield.

Gyome, Master Chef's second ability counts all nontoken creatures that entered the battlefield under your control this turn, even if some or all of those creatures are no longer on the battlefield, no longer creatures, or no longer under your control.

You can activate the last ability even if the creature is already tapped.

You can't sacrifice a Food to pay multiple costs. For example, you can't sacrifice a Food token to activate its own ability and also to activate Maraleaf Rider's ability.

Food is an artifact type. Even though it appears on some creatures, it's never a creature type.

Whatever you do, don't eat the delicious cards.