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

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.

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

You can cast Spider Food without a target just to create a Food token. However, if you do choose a target, and that target is illegal at the time Spider Food tries to resolve, the spell won't resolve and none of its effects will happen. You won't create a Food token.