Viscera Seer is a sac outlet that will let you scry.
Ashnod's Altar will get you some colorless mana when you sac a creature.
Spawning Pit isn’t a great one, but will make tokens once you use the other ability.
Altar of Dementia in case you want to mill yourself or an opponent.
Carrion Feeder can become huge by sacrificing creatures.
Vicious Offering can act as a good piece of creature removal around indestructible if you kick it.
Attrition by sacrificing and paying 1 black it will act as removal.
August 13, 2019 1:35 p.m.
Cards not mentioned yet
Free sacs in your colors:
Greater Good , can potentially draw a lot of cards
Blasting Station , could work potentially if you can gen some creatures
High Market , not the best card but still free.
Not free but still might work:
Skullclamp , can be great in certain decks
Thornbite Staff , might have a synergy somewhere that can give you infinite triggers.
Not in your colors but honorable mentions:
August 13, 2019 2:12 p.m.
I would say stick to just having Viscera Seer , Carrion Feeder , Altar of Dementia , and if you really need another pick one from the cards listed in previous comments. Having too many sac outlets can be a problem. I have found that 3 or 4 does it for me and the 3 I mentioned do it best