I used Tribestan too as a stand alone. Didnt stay on long enough to notice any mass gains but sexdrive was through the roof and the volume of "man juice" seriously increased.
I tried another brand, think it was U Labs... the only effects I got were negative. One of my nuts started to get a dull ache after about four days, this continued for another couple of days then I started to feel a pulse in my prostate (like it was about to start swelling). I stopped taking the stuff straight away and all returned to normal. I used Tribestan since and never had the same problems, just increased sex drive and improved mood.