I actually just started about the time Planeswalkers 2014 came out too. I like your deck's synergy. However, two things you should look at are you converted mana cost (CMC) and your land count. Think of your CMC as a stairway, it should go lower the farther right you go. Your deck has equal amounts of cards costing different mana amounts. Instead, you may want to try having 8-10 one drops, 15 or so two drops, 8-9 three drops, 4-5 four drops, etc. This will prevent your hand from clogging with unusable cards early game. It is also recommended that around 40% of your deck should be lands, so cut them from 30 to around 23-24 and it should give you some wiggle room to add or remove cards at will. Here is my deck Aurelia Rises take a look at card counts and see what I mean. Hope this helps.
Looking at the deck, I don't know how much money you want to spend on the deck but.
Doom Blade > Ultimate Price - Doom Blade has more targets to hit than Ultimate Price, a lot of decks are playing mono-colored creatures like Thragtusk , Angel of Serenity , Desecration Demon , Ogre Battledriver , and Augur of Bolas (tried to get one from each color). But htey're also running Boros Reckoner , Huntmaster of the Fells Flip , Voice of Resurgence , Prime Speaker Zegana who you can't hit with Ultimate Price but you can with Doom Blade
Dreadbore > Auger Spree - This is for all the pesky Planeswalkers Jace, Architect of Thought , Ral Zarek , Vraska the Unseen , Domri Rade , Garruk, Caller of Beasts . Even if your opponent isn't running Planeswalkers it still hits creatures.
Rakdos's Return > Stab Wound - While I can kind of see what you're going for here with the Stab Wound to try to deal free damage to your opponent, you're wasting your turn 3 to play this card and your opponent will just say "ok guess I'm chump blocking his attack with this creature now." Rakdos Returns does damage and it gives you card advantage over your opponent.
Sire Of Insanity > Master of Cruelties - This one is kind of hard for me to say. While Master of Cruelties is the best blocker in your deck, that's the only purpose he's going to serve "But Shinkari he lowers my opponent's life down to 1 if they don't block him." This is true, but in a creature heavy format this will rarely happen unless you board wipe your opponent, and since you're running only 1 Mizzium Mortars and 4 Master of Cruelties I doubt that it's going to be the case. Another problem with this card, especially in this deck, is that you have these Unleashed creatures who aren't going to do their main purpose, attack, so that you can maybe get the Master of Cruelties ability, while they sit back and can't block. Sire of Insanity is an insane card, since you're red-black you will more often then not have a better top-deck than your opponent, since you'll have burn spells, some card draw, and also scary creatures. And playing this guy late game will already give you a better board position than your opponent.
You can only run 4 Rakdos Guildgate .
I hope this helps and sorry if it was a wall of text. +1 because I love Rakdos, favorite guild along with Simic.
Sorry about the triple post, but just noticed you have 6x Rakdos Guildgate . You can only run 4 of these because it is a non-basic land, just like the ones I mentioned above.
Not bad. I would however-
+1 from me. Also added as a friend, I'm a supporter- er player of Rakdos.