I'm coming to this after a few days, so I have the benefit of reading some of your replies. My feedback below is split between objective and opinion-based.
Objectively, you are not discussing TRT. TRT is a treatment for hypogonadism, which is both a deficiency in testosterone and the presentation of clinical symptoms. You meet neither of these criteria. What you are considering is recreational testosterone use. Being clear about that is central to making decisions in this area.
Also objectively, you should take these dose ranges with a grain of salt. There is substantial inter-individual variation in the injected dose and the resulting serum value. Both medical literature and the clinical rule of thumb put this number around a factor of 3. However, on average, 100 mg/week is the top of physiological testosterone level.
With that point in mind, here's the transition to the subjective: what do you care what your testosterone level is? I don't mean that rhetorically. What is that number going to tell you that informs your decision-making? What will you change if it's 800 versus 1300 ng/dL? If you're honest, I think you'll answer that you don't have any idea.
You're asking for the correct dose of the wrong medicine. You're here asking what the right amount of Tylenol is to fix your dry skin, and there is no correct answer aside from, "you're asking an ill-conceived question." Motivational drive is influenced by testosterone, but it's in the context of someone with a baseline motivation level noticing a drop when testosterone levels decline. Your baseline motivation is what you're identifying as problematic; testosterone will not affect that.
This isn't finger-wagging. I take testosterone specifically to put my levels higher than they would otherwise be as an early-40's male. It's partially vanity, largely a refusal to give up the hobbies I enjoy, and very candidly an inability to come to terms with the reality of getting older. It's not a great reason, but it's a clear reason, and it tells me how much to take: enough that I can go to BJJ, lift, and play recreational sports such that soreness doesn't impact my daily life. Then, I don't take anymore.
That relatively modest amount comes at a non-trivial cost. I pay out of pocket for bloodwork every few weeks and organ imaging once every year. I take medications to manage hair loss, blood pressure, and blood lipids. Because I take finasteride, in order to deal with elevated hematocrit, I can't donate my blood so I also have to pay for therapeutic phlebotomy; this is necessary because I've got a history of idiopathic clots that predates testosterone use. That means I am still on Eliquis even though I could probably otherwise drop off. I am also now fairly obligated to exercise, because if I put on some fat then I'll start to aromatize more and have to chase that with an inhibitor, and those are hard to dial in against a moving backdrop. So when I'm on call, I have to go outside to jump rope like a fucking idiot at four in the morning. It's not all that fun in December.
Do I have to do all of that? No. Do I have to do all that so my health and happiness aren't all worse off? Yes.
What feedback is going to tell you that you've had enough? When you get six months in and realize you still don't want to go to the gym? But you're inherently lazy -- you'll realize it's momentarily easier and less unpleasant to stay on TRT than it is going to be to go through the process of going off and restoring natural function. And maybe it comes back fully, or maybe it comes back decreased. Maybe you're one of the unlucky ones and it remains depressed for years or permanently.
You're asking about starting something that's going to take a lot more work to do right than just going to the gym. This is why everyone gives the advice to fix everything and have a solid foundation of diet, sleep, and training before getting into this. There is no free lunch.
Replace a tasty thing with some cottage cheese or a protein shake, get a caffeine-laden pre-workout to fake some motivation for the gym, and just go. It's way easier than what you're signing up for.
