X2 on hcg during and not after, why bring your nuts back up to par when you can prevent atrophy in the first place.
Anastrazole (arimidex) is an AI and as such you should run it alongside your cycle regardless of any gyno symptoms, having elevated estrogen due to aromatisable steroids can cause worse problems than gyno, most notably liver damage. Keep some additional nolva handy as that will help take care of any gyno symptoms during cycle.
You must run AI. Find a comfortable dose, you can up it accordingly. You don't want to take too much and bottom out your estrogen but you don't want high estrogen levels either, in fact you can experience similar sides such as libido loss with your estrogen on either side of the spectrum. I would begin with .5mg EOD or .25mg ED and go from there. People that think high doses of test make you bloated are probably the ones holding shitloads of water due to high estrogen levels from not running AI.
As to what the above poster mentioned, after several weeks myostatin expression limits continual gains. Typically this is the point at which you either swap around compounds or up doses to continue progress. In a nutshell he is suggesting starting with a lower test dose and upping it over time.
You are a bit young at 19 but whatever, just know you run the risk of damping your endocrine system development. If you start now, you may be in it for the long haul, but with TRT for older males being so popular nowadays anyway, who cares. You got good stats for your age.