If you're feeling like combos:
Mikaeus, the Unhallowed can make a MESS with some persist creatures thrown in.
Lavaclaw Reach and
Ceaseless Searblades works well. Lavaclaw is a cheap (last I checked) dual land in your colors so that helps too.
I enjoy
fling effects, and they give you sac outlets to trigger your general.
Bloodshot Cyclops is in color and repeatable.
ETB effects like
Pandemonium or
Warstorm Surge would be terrifying for your opponents to play against. (Sac a couple creatures, burn you for 15,18,21...)
Killing wave might be worth running in that regard. If you pick only 2 cards from what I've listed, pick these two.
Going back to combos:
Sekki, Seasons' Guide goes infinite with Pandemonium. (The gatherer comments explain it, if it's not clear. I know it certainly wasn't for me at first) Up to you if that's your type of thing or not.
Some generally nice cards to have/cards I personally like to run:
-I really like
Elixir of Immortality. I include one in all my EDH decks, but it's questionably necessary. At worst it gains you 5 life.
-Wrath effects; I like to include one as it give you an answer when the board locks up or gets too scary.
Damnation would, of course, be ideal, but cheap options are out there too:
Life's Finale is my usual.
-You're running black;
Exsanguinate is super awesome, especially in multiplayer (which EDH almost always is) where it can be a kill spell and/or just an "I don't die now" spell.
-On a similar note: you're running red;
Insurrection is often just called "I win." It's really powerful, up to you if you want to run it or not.
-A tutor or two is nice to include.
Diabolic Tutor is probably the standard.
Demonic Tutor cost less to play and costs more to buy! I try to avoid running too many of these (black has a ton) as it can make the deck too repeatable. You're a lot less likely to run into a completely random "this interacts with this interacts with this interacts with..." which, at least for me, is what really makes EDH fun.
-Mana fixing & the like: I like
Darksteel Ingot (indestructible is awesome, someone can and will blow up all the artifacts at some point) and
Spectral Searchlight because: hooray politics (it's EDH after all)
Hope I haven't thrown too many options at you. Have fun and enjoy my favorite Magic format!