Viscera Seer is one of the nuttiest sac outlets around. And, after you sacrifice everything, cast Living Death. Ashnod's Altar is also an outlet I can't recommend enough. It's not Phyrexian Altar, but you'll find lots of uses for it. Blood Artist (and similar effects) fits the sac theme.
https://tappedout.net/mtg-decks/edh-skeletons/?cb=1575188895
Birthing Boughs makes skeleton tokens. Taurean Mauler is a great skeleton. So is Chameleon Colossus. Adaptive Automaton is made to shore up tribal decks like these.
Non-Budget: