I know I'll take some heat for this but building a budget PCC is folly if you intend to use it in competition. I've seen way too many not deliver the performance and reliability needed for a match. If the PCC is for causal fun that is another story.
I subscribe to the "buy once, cry once" approach and as such the barrel, bolt and buffer systems in my PCC's are all JP with triggers being Hyperfire or POF. There are certainly other high quality options out there but the key is quality, proven components if you are wanting serious results.