Hi there and welcome to the forums!
Since you are new to budgies, your priority right now should not be breeding as for doing so responsibly, a person must have a very good knowledge and real life experience in budgie ownership. Besides this, the necessary research should also be made in order to ensure the welfare and safety of the breeding pair and any incoming chicks.
First of all, the new budgie you got should have been quarantined in a different cage and room away from your current pair.
This is done as a preventive measure in order to avoid any potential illness carried by the new budgie to be spread to your pair.
Please take a look at this link and separate your new female right away :https://talkbudgies.com/new-budgie-ar...necessary.html
Also housing two females with one male is also a recipe for disaster and you are already experiencing this with the fighting between your females.
When housing an odd number of budgies who also happen to be mixed gendered, vicious fighting can be expected and an immediate and permanent separation needs to be done in order to avoid bloodshed and casualties. Please get a second cage for your new female.
This link will also be useful: https://talkbudgies.com/articles-gene...en-flocks.html
The decision to breed comes with a whole lot of responsibility and commitment, the lives of the breeding pair and the chicks are depending on you and the response you give if/when faced with adversity.
Things like being able to tell if your breeding pair is in good health and top physical condition to go through breeding; when a hen is expecting an egg or if she is showing the first signs of being egg bound; when a chick is having developmental problems, not being fed or showing signs of dehydration;
when there is aggression, abandonment and neglect of the chicks and it's solely up to you to feed and raise the chicks. The ability to detect early on and solve these issues can truly make a difference on the outcome of your breeding journey.
The first step really is to take a more active role in getting to know your budgies, to study their behaviours, learn how to read and decipher their body language and how they interact with you and among themselves, in short to gain experience by taking a real interest in your budgies and being really open to learn by watching them. This valued experience combined with the resources found here at Talk Budgies will be of benefit to you and when the time comes to that are fully prepared and ready to allow your pair to breed, you can consider doing so.
Read the information on this link also: https://talkbudgies.com/budgie-breedi...s-new-old.html