It's difficult to give an opinion without knowing the basics... Previous experience, muscle level, and current BF, what are you looking for as a result...
But to start, and as others have mentioned, unless you're clear about the reliability of that PRIMO (the active ingredient has been in short supply for a while) and 300mg is not enough... I'd go for a 400/500mg Testo monocycle.
Also, from the experience of a veteran, it used to be common to mix a little bit of everything to get the benefits of each substance (250T+100 Deca+Winstrol... or 250T+200 Primo) because that's what was dosed in pharmacies for medical use, not sports use, and it was sold in pharmacies without problems... And the truth is, besides not knowing where the possible negative effects are coming from, a 500mg Testo monocycle is more effective and controllable if you're looking to gain mass.
If you want, you can add HG, but if you're not a pro... I don't know if the price is worth it.
But as I said, without more details, it's hard to give an opinion.