I just test fired my first ever ar-15 pistol build... couple problems i had.... light hammer strikes... and it consistantly will not cycle the next round.. so first off... who can tell me reasons for why this might be happening...  
its a spikes lower,  YHM clamp on gas block, phase 5 tactical hex-2c complete pistol buffer tube kit. and a 7.5 in 5.56 faxon firearms Barrel
Could it be the gas block? could the buffer spring be too powerful ? any ideas

Did you check the head spacing? That could be the cause of your light primer strikes. I would also try a different bolt carrier group. See if your hammer spring is installed correctly and make sure it's not a reduced power spring (I doubt that's the problem).

As for your cycling issue, try to re-align your gas block or if you can, try a different gas block. In rare cases, the gas port diameter can be too small - I bought a barrel last year from a reputable company with this issue. If you're using a mil-spec carbine buffer spring (about 11" long) then that should't ever be the problem.