Recently I have updated my deck to being straight mono-red instead of atarka red.
Reason for this is because i find atarka's command to be stuck in my hand quite a lot.
I also run 19 lands including 2 caverns and 2 contested warzone which makes the green source quite inconsistent.
This is my current list:
4Foundry street denizen
4Mogg War Marshal
2Cavern of Souls
2Contested War Zone
3Leyline of Punishment
3Eidolon of the Great Revel
3Smash to Smithereens
I have been very impressed with Heelcutter. It's perfect to get through a big blocker but also very usefull when playing against a controlplayer with a lot of removal. If they boardwipe, dash the heelcutter, hit them for 3, then next turn we can just deploy our small dudes again keeping the heelcutter back. It's also very effective at taking out planeswalkers like future format Jace. I may cut a tormod's crypt for a 1 off kari zev's expertise as that card seems very good against dicey matchups like Tron resolving a wurmcoil engine.
In general I believe Goblins is a deck that is perfect for goldfishing. However the most important fact I have to state about goblins is playing smart wins more games then just rushing blindly into your opponents. When the opponent floods the board with creatures but you got him at 6, just wait. You know you're not gonna get to him but more importantly, he's not gonna go after you anytime soon because he knows about goblin grenade. If they don't then congratz, you just won. As long as they are not confident they can hold off your crackback, they're not gonna do anything which gives you time to draw grenades, bolts, firebrands and fanatics.
The hardest matchup I feel are green midrange decks that play any form of lifegain/protections like kitchen finks, burrenton forge tender, courser of kruphix etc... This is why I put in leylines and eidolons against them. It's still a hard matchup but when you put a leyline down before turn 1, they have an unholy fear for everything you do as they count on the lifegain to keep themselves in the game.
Anyway, let me know when you think of the list and sideboard as all tips are very welcome.