Alekhya With a properly guided HRT regime, you should get a fair bit of breast development naturally. A thumb rule is you will get to one cup size lesser than your closest female relative - sister or mother in that order. But it takes upto 3 years for full breast development under HRT alone. Implants can speed up the process.
However implants cannot give the other secondary breast development like development of the nipple area. That will come through HRT alone.
A common mistake made by many girls is to go in for implants a few months into HRT. Since there is continued growth of underlying breast tissue with HRT, this results in misshapen breasts. Many girls are then forced to do corrective surgery to reduce/remove the implants and some underlying breast tissue.
Spare yourself the torture and your money! IMO, don't do implants immediately if you intend to do HRT. Wait for 2/3 years of HRT, see the results and then decide whether you need implants. If for whatever reason you are not doing HRT, then yes implants are the way to go.
Just my 2 cents.