After many attempts, this is my very last build of a Gruul deck:
...
From my previous version, I completely wiped off the subtheme AURA (diverted to my new Naya deck "Aurora baestialis") focusing on Kiln Field and trying to develop the low part of the curve, inserting 5x1mc creatures (choosing from which can have a potential synergy with Doubling season) and 2xCultivate that triggers the Kiln Field effect and guarantees a mana acceleration.
Maybe I have too few beasts now, but I've obtained a very good win/loss ratio so probably the deck works well in that way.
Just for curiosity, I have obtained 8 win/2 loss but in all 10 matches I didn't ever draw "Doubling season", that in my plan would be the strongest card of the build (as well as my obsession).
This deck seems a little "all over the place." It seems like you wanted to have a bit of everything and as a result the deck got spread a little thin. Perhaps just try and figure out what it is you want the deck to do and concentrate on working towards that end game.
If you were wanting to exploit
Doubling Season, perhaps try ramping into it quickly then use your big fellas to exploit it. You're not always going to draw it because of it being a two-of, but your big guys should help you win anyway. In this case I would remove a lot of the low end stuff such as
Kiln Fiend and replace it with card draw, ramp and chumps to help you survive until you can get your fatties out.
If, however, you were finding you were winning before reaching the big guys and doubling season, then perhaps focus on having the small guys win quickly. I can't give you too many tips here without turning your deck into my Gruul deck so instead I'll just
point you towards my one as inspiration... hopefully.