Scavenger's Talent's level 2 class ability will trigger when you sacrifice it. If you sacrifice other permanents at the same time, it triggers for them as well.

There's no restriction on how many Class permanents you can control, whether they're the same or different classes. Each Class permanent tracks its own level separately.

Each Class starts with only the first of its three class abilities. As the first level ability resolves, the Class becomes level 2 and gains the second class ability. As the second level ability resolves, the Class becomes level 3 and gains the third class ability.

You can't activate the first level ability of a Class unless that Class is level 1. Similarly, you can't activate the second level ability of a Class unless that Class is level 2.

Gaining a level won't remove abilities that a Class had at a previous level.

Gaining a level is a normal activated ability. It uses the stack and can be responded to.

Each Class has five abilities. The three in the major sections of its text box are class abilities. Class abilities can be static, activated, or triggered abilities. The other two are level abilities, one activated ability to advance the Class to level 2 and another to advance the Class to level 3.

If you sacrifice a permanent as part of casting a spell or activating an ability, Scavenger's Talent's level 2 class ability will resolve before that spell or ability.

The creature card you return from your graveyard with Scavenger's Talent's level 3 class ability may be one of the nonland permanents you sacrificed.

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.