The core idea here is that Welder is tolerably good right now and so are Sulfur Elemental and Jester's Cap effects. We're presumably looking at a Mentor and combo meta. To deal with turn 1 kills, you need blue. To deal with Mentor, you need red and/or fast kills. Lackey is not good right now: you can't rely on a 1/1 connecting and running enough removal to change that risks having a bunch of dead cards against combo. So we're going to run strong effects like Tinker, Trinisphere, and blue draw. To deal with the gaping weakness to aggro Shops, we're going to maindeck Rakdos Charm and Dack. This has the side-effect of giving us a solid game one against Dredge.
Goblin core:
4 Goblin Lackey
4 Goblin Matron
4 Earwig Squad
1 Gempalm Incinerator
1 Goblin Dark-Dwellers
2 Goblin Welder
Disruption:
4 Rakdos Charm
2 Dack Fayden
1 Sulfur Elemental
1 Goblin Sharpshooter
Good cards:
1 Demonic Consultation
1 Demonic Tutor
1 Vampiric Tutor
1 Ancestral Recall
1 Brainstorm
1 Time Walk
1 Treasure Cruise
1 Tinker
1 Thirst for Knowledge
1 Trinisphere
1 Wurmcoil Engine
Mana Base:
1 Mox Emerald
1 Mox Jet
1 Mox Pearl
1 Mox Ruby
1 Mox Sapphire
1 Sol Ring
1 Mana Crypt
1 Black Lotus
4 Cavern of Souls
1 Mountain
3 Badlands
3 Volcanic Island
4 Bloodstained Mire
1 Scalding Tarn
1 Strip Mine
Sideboard
1 Dack Fayden
1 Shattering Spree
1 Grafdigger's Cage
1 Null Rod
2 Mindbreak Trap
4 Mental Misstep
2 Pyroblast
2 Illness in the Ranks
This has done reasonably well, but not great, on Cockatrice. Game one people tend to be caught very off-guard by Goblins casting Ancestral Recall or Dack Fayden. Post-sb, there's a lot of removal and Lackey is not a good card. Earwig has unsurprisingly overperformed. It's plausible that something like Control Slaver with a random Earwig Squad would be a superior variation on this. Alternatively, this might be entirely the wrong route to try as 5C Shops can support both Welder and Cap alongside a better aggro clock already.