A bra under a cami is fine Michelle. I wear them frequently.
For my boobs I have used knee high stockings and rice. You will need 2 pair of knee high stockings and 1 kg of long grain rice.
Place one knee high inside the other to make a double layer and do the same to the other pair. Measure out 400gms (14bB cup) or 500gms (16B cup) of rice and pour into each double pair of knee highs. Pull the knee highs tight around the rice and tie off with some big knots. These knots make a good nipple when place in the bra. Cut off the excess knee high above the knots and there you have a nice pair of boobs. I have been wearing my pair for the last 10 years.