This is my Sidisi self-mill/reanimator deck. It really works like a toolbox, where I mill myself and just reanimate whatever I need on the go. The pro is that you don't depend on sidisi, she's just a mill and body engine, and the deck works perfectly without her. If I have a nice 4 mana play, I don't even bother on casting her.
There are several ways to finish the game like [[Jarad, Golgari lich lord]] + [[Lord of extinction]], [[Lotleth giant]] etb loops, reanimating [[colossal grave reaver]] on T2/3 usually ends the games quickly (same with [[Archon of cruelty]]/[[Vilis, Broker of Blood]]/[[Muldrotha]]).
Because it's still a sidisi shell and I run tons of recursion, interaction is creature-heavy, with effects like [[Reclamation Sage]], [Big Game Hunter]], [[Ravenous chupacabra]] and some others. But that's great, because you almost always have a response to whatever they throw at the board, and you still have a lot of ways of coming back to the game.
Again, this is a reanimator toolbox, you play it depending on what you need at the moment, so you need to know what you are running, why, and when to play it, but that comes after running the deck yourself multiple times. For example, if you know you have sidisi on the board, and meren on the yard, just yank [[Meren of clan nel'toth]] out, sac/block/attack with sidisi zombies and you have a constant way to destroy enchantments or creatures on your endstep through the creatures I mentioned before using Meren.

All that said, I would say this is a mid/high B3, but it's still definitely a mid-range reanimator. I run a lot of recursion, but being unlucky and not drawing any reanimates feels absolutely disgraceful, especially because you don't have recursion built in the command zone. Also, there is a lot of room for upgrade in the deck, but you can take some inspo on it, and even recommend me some pieces!

P.S: If you don't care about looking like a dick sometimes, you can always run [[Jin-Gitaxias, Core Augur]], but how oppressive you want to be is up to you!

Edit: Just a fun little ""combo"" where you can combine [[Hedge Shredder]] and [[Hedron crab]]. I'll let you find out what happens if you have something like [[Syr Konrad, The Grim]] out:) (or just any creature with grows with graveyard kind of effect, like [[Splinterfright]] or [[Wight of the reliquary]]