First, I can say from my personal experience that you can ignore the people saying 100 won't do anything. If your natural test is low, getting back into the mid-normal, preferrably high-normal range can make a big difference. My libido improved, I sleep better, feel better overall. But, 100mg does shut me down, so I've added HCG. I'll be going back for a retest in a few months, and if I'm just in the 500ish range, I plan to work on my endocronologist to up the dose to 150/200 per week to get into the higher normal range, and I respond better with 200mg injections, just want them weekly not every other..., then will do my own stuff from there periodically... 100 mg/week is the typical TRT dose, but it can vary quite a bit depending on what works for the patient, and what your natural levels were before they started dropping off, so you'll need to work with your doc to find an appropriate dose with manageable sides, that gets you the most improvement.
As some background, I was very active on the boards back in 2001-2003 under a different name ("the good old days", lol, from before AAP was a mod and had a much more interesting screen name, Mr X, Nelson, Radar were all around then, don't think Radar was a mod, and he was more active on other boards, but whatever, QV sigh... ) , so even though it may look like I'm a noob with 3 posts, that isn't the case.