Just a few cards I think would work in your deck well. You might have some of these in it i don't quite remember what all you had, any of the Blue devoid eldrazi work i think i saw a few in yours so i didn't put them here, pretty much any of the eldrazi would work great. The cards i would really suggest are the Sage of epityr, sage owl, cryptic annelid, they are great because they let you know what is coming up soon. you can play one and be pretty much sure if its worth it to activate your commander or stack so you draw the spell you want and not the creature, plus they then are able to be sacrificed to your commander. Most of the other stuff i just think would synergize. Cauldron of souls lets you get something you sacrifice right back, intruder alarm lets you keep using your commander by untapping it. I tried to just go for pretty budget cards not expensive ones like Glen Elendra Archmage. I know your commander doesn't hit legendaries but if you cast him normal and are casing alot of instants and sorceries Talrand gives you alot of fodder for your commander. This isn't all cards you need just some things I think would work. I know you have a lot of control spells in the deck so I didn't really put any in this list.