Kels, Fight Fixer

If you sacrifice a permanent as part of a spell or activated ability's cost, Kels's middle ability will resolve before that spell or ability.

While resolving Kels's middle ability, you can't pay blue or black mana more than once to draw more than one card.

Kels's middle ability is a triggered ability, not an activated ability. It doesn't allow you to sacrifice a permanent whenever you want; rather, you need some other way of sacrificing permanents, such as Kels's last ability.