This guy is on doctor prescribed Test C at 100mg E7D and has stated that and this is also the TRT forum.
You're not replacing what you were making, you have obviously now higher T levels than what your started with however keep in mind your HPTA is shutdown. 100mg is a good starting point for TRT. Your doctor should be requesting blood tests soon to see where this puts you at. Throw up your bloodwork before you went on TRT and your current bloodwork.
Has the doctor prescribed you with an aromtaise inhibitor, preferably Arimidex (Anastrozole)? You may or may not need it, but bloodowork will confirm.
In regards to you initial question, how big and strong you get is dependant on your training and diet. 100mg of Test per week is a true TRT dose, I would aim for the 1000ng/dl mark if your doctor wants to get you there. There will eventually become a point where 100mg won't provide as fast and drastic changes in strength and body comp, after all it is a true TRT dose. Dialing in your TRT protocol is paramount before you start raising the dose/adding in other compounds for a certain time period AKA what we call a blast.
I strongly suggest reading up threads in the TRT forum to get an idea of what involves TRT, the pros (many), the cons (few, dependant on other life factors too) so you can get a good idea on the topic.