I don't know if there are any actually engines in standard right now seeing play. I suppose you could do
Sanitarium Skeleton +
Vampiric Rites to net 1 card and 1 life for 6 mana. Bit slow, but it works.
Tireless Tracker is the primary card draw card in Human bases strategy, and
The Gitrog Monster is the major sources of card draw right now.
Black usually uses
Read the Bones or
Succumb to Temptation (only reason to use Succumb is for instant speed to hold up removal). Red has
Tormenting Voice (which pairs well with all the Madness cards in Standard).
If you go Blue Black, there's potential for a Tempo Zombie Tribal deck based around self mill, graveyard recursion, and psuedo card advantage.
Gisa and Geralf gives card advantage by letting you recast cards from your graveyard, and
Relentless Dead gives card advantage by never fully dying and bringing back other zombies. None of these are really draw engines, but they give card advantage so that's why I'm including them.
In Blue/Red Spells, there are lots of draw options, but I've seen
Bedlam Reveler come up as the most powerful draw spell. The idea of course being to have an empty hand when casting the Reveler so you can just draw 3 for free.
I hope you found this helpful. Good luck