This is perfect. Krenko was my first commander deck too, and it absolutely is a great deck to start with. He is still my favorite Commander to date. So I know a lot about what cards you'll be wanting.
Win ConditionsLet's start with the win conditions, and then work backwards. You already have
Thornbite Staff, which is great. You generate infinite tokens with any sacrifice outlet (
Skirk Prospector,
Goblin Bombardment). If you want the combo path,
Umbral Mantle also works with some cards (
Skirk Prospector,
Ashnod's Altar,
Mana Echoes). And then there's
Breath of Fury. All you need for this combo is a global haste enabler, and an opponent who can't block. Enchant a goblin token, and attack the player who can't block (have all other goblin tokens attack other players). With the additional combat step,
Breath of Fury snaps on to another token, and all creatures untap. Tap Krenko to get more goblins, with haste (thanks to the global haste enabler). Repeat for infinite combat damage.
For any of these combos,
Gamble will be useful (as is
Imperial Recruiter, but he's pricey).
A lot of times, you can also win with massive combat or burn damage.
Shared Animosity,
Coat of Arms,
Obelisk of Urd, and
Eldrazi Monument will all help you win with combat damage. For burn damage,
Goblin War Strike,
Mob Justice,
Purphoros, God of the Forge, and
Furystoke Giant can all end the game for someone (Furystoke is also a one-sided boardwipe sometimes).
SupportIn all cases, you want lots of creature tokens. So let's do that; build a token army. When playing this deck, keep in mind that your tokens are not expendable early on. Try to keep your early goblins
alive (going from 2 to 4 to 8 to 16 goblins isn't as good as 3 to 6 to 12 to 24). So let's build this army.
Thousand-Year Elixir let's you get two uses of Krenko per turn, and doubles as a haste enabler.
Goblin Lackey and
Goblin Instigator can also get you more goblins in the early game. You also want haste enablers, lots of them. Prioritize global haste (
Goblin Warchief,
Goblin Chieftain,
Fervor), but just giving Krenko haste could be enough (
Goblin Motivator,
Lightning Greaves,
Hall of the Bandit Lord).
Mass Hysteria is a good haste enabler, but be warned; it may help your opponents more than you.
Generator Servant is excellent, and should go in every red deck where your commander benefits from haste.
Mana RampEven though you have a low curve, you'll still want some mana ramp. With goblins, you get access to some pretty unique stuff. You already have
Skirk Prospector, but let me suggest some more.
Battle Hymn and
Brightstone Ritual give crazy amounts of mana.
Infernal Plunge gives a quick boost. While not as good as the others, it's still useful.
Cheering Fanatic gives light mana ramp, but doubles as a low-cost goblin.
Chandra, Torch of Defiance gives mana ramp, as well as some other relevant abilities.
Ruby Medallion is a staple in mono-red. And lastly,
Mana Echoes will give you more mana than you'll ever need (also goes infinite with
Umbral Mantle).
"Card Draw"Red gets shafted for card draw effects (at least you have
Skullclamp), so it relies on "red draw".
Dark-Dweller Oracle and
Chandra, Torch of Defiance sort of give card draw. You can also try
Wheel of Fate,
Winds of Change, and
Reforge the Soul.
RemovalLast little bit, you need ways on dealing with threats.
Abrade,
Outnumber,
Chaos Warp,
Goblin Assassin,
Goblin Trashmaster, and
Goblin Welder.