Lefty shooter here who is now suppressed and holy cow does this suck..

1. What brands, all ive really seen is stag but who makes the good stuff for lefty?
2. What else do I need lefty? BCG only? Bolt only? Whatever I need recommendations for that as well..
3. After this is done will something like the gemtech suppressed carrier be enough? or should I still get an adjustable block? My only issue is I usually run midwest Super Slim guards..

Thank you in advance. I will probably be swapping 3 or 4 rifles over to this so, trying to get my info and knowledge in here haha.

I'm a lefty -- why go to the expense of left-eject parts?  My ARs are all "standard," with a couple ambi pieces (safety, mag release).  In some ways the standard AR is better for lefties than righties.  

If you are trying to diminish the suppressor blow-back, shifting to left-ejection won't help much.  Most of the gas from my suppressor is coming from the gaps around/under the charging lever -- in other words, straight back, so moving the ejection to the left side won't help much.

Finding parts (including reasonably-priced parts) for left-ejecting ARs is also a witch.

Left handed barrel extension to aide in the bolt to go fully into battery.  These chamfers also meet the chamfers installed on the bolt lugs on a left handed bolt.

http://www.keystoneaccuracy.com/lefthandedspecialist.html

I'm leftie.
I use a Griffin armament sn-ach charging handle and a Lantac E-BCG. Both are meant for supressor use.

I imagine a superlative arms, bleed-off adjustable gas block may help as well.

You could go piston as this would help with gas going back through the barrel and into the upper receiver.

I have two left handed AR-15's that I have built. One was with a WOA barrel with an ambi extension and the other with a FN chromelined take off barrel with a normal extension. I couldn't tell a difference between the two barrel extensions.

Now if your going to build a left hand rifle you need a left hand upper receiver and left hand bcg. Stag makes these parts as well as Red X Arms upper receiver, CMT upper receiver, there are also other companies that make some left hand ar parts.

I use the Radian Raptor SD charging handle, it works in both right hand and left hand upper receivers.

You can't use a gemtech bcg if you plan on using a left hand upper receiver. I'm using a Superlative Arms gas block on both my left hand and right hand suppressed AR's and they work just fine.