It is totally possible to breastfeed, at least to some extent, even though you have not had a baby. Most women are able to produce some milk but oftentimes not enough to solely breastfeed, so it is normal to have to supplement at the same time. If you have nursed a baby before it increases your chance of producing enough milk, but if you need to supplement it is still worth it to build up your milk supply and breastfeed. If you think about breastfeeding from a relational point of view as opposed to only for sustenance then you are more likely to feel that you have succeeded and it may make it more worth the work involved. Breastfeeding, beyond being the best nutritionally, for the baby is key for comfort and bonding of the baby and for you it will cause you to release oxytocin which will increase your patience and attachment to the baby.
Breastfeeding is a beautiful gift to both the mom and the newborn, but for many women it is far from easy. Before the birth is the time to prepare for breastfeeding and prevent any issues that might ensue.