Kruber is great! I love halberd also and play 99% of the time with it If you are lvl 12, just play and do not waste dust on crafting orange items, just play, craft normal halberd from time to time (every 50 power level difference) and once you will be able to play on Champion without a problems you can try swift slaying on it as a trait. I use it and it is great.
Just try other items and use whichever you like and have fun with it, up to Champion every weapon is viable, Legend is different.
For now you can also stick to Mercanery, he has great damage buffs and you will have more influence in low level games
Ah, I am 30lvl Kruber Legend player