What I can say is, pick one modeling software to be comfortable with and study and practice as much as you can with it. You have Cinema, Maya, and Max. They can all do the same thing but what they differ in is “how to get the same result”. For example, you want to make a model of a dragon or whatever. The three programs you have will be able to do it for sure, but there are different interfaces and buttons to click and press.
Zbrush is something that you’ll want as a program to give detail to the models you create in any of the 3D modeling programs. As of now, you can actually “retopologize” any model you import in Zbrush. For example, you’ve made a dragon with 3DS Max and you sent it to Zbrush for detailing. After you’re done giving the model some details like maybe dragon scales, you’ll notice that the topology (imagine your dragon made as a wireframe, ideally they form squares to make animation easier) of your dragon got messed up and they turned into a nightmare where you can’t clearly see where each of them connects. In the latest version of Zbrush, you can simply use “DynaMesh” on this messed up model and its topology will fix itself to become clear and mostly form squares again, making it easier for you to animate back in 3DS Max. Actually, some people skip modeling stuff in 3D modeling programs like 3DS Max and head straight to Zbrush and “sculpt” whatever they want in there because of the new retopology ability of Zbrush. Zbrush just doesn’t have the feature to animate models (as far as I know) so you will still need a 3D program like Max for the animation part.
Anyway, since you said your parents bought all of these for you, you must be really lucky! It’s just that you could’ve saved the money and just chose one 3D Modeling program to go along with Zbrush. I’m a 3DS Max person myself and I haven’t tried Cinema or Maya, so I can’t really say which one is the best among them, so maybe you’ll have to ask someone who has tried all of them out.
I really hope once you’ve made your decision as to which program to use for modeling and animating, your parents can get a refund for the other two 3D Modeling programs. If they can actually get their money back, I advice you to ask them to buy you training material instead. I recommend, just for starters, those training videos from Lynda, Eat3D, and Digital Tutors.
Since you have no experience making any 3D models at all, I really recommend you to buy even a book for total beginners for whatever 3D Modeling program you choose as one of the most important things to start with is being comfortable with how you control that piece of software without getting lost and confused.
My Personal Recommendations:
3DS Max 2012 - Just because I’ve been a Max user since my highschool years over a decade ago. I haven’t tried Maya or Cinema, but from what I’ve read and what people told me when I asked for the same advice before, they said Maya is a little harder to learn than Max, but it’s better with fluids (maybe they’re talking about particle simulation).
Zbrush 4R2 - this is the tool to use for adding details and all sorts of nice touches to your model. You can actually use it to paint your models as well! As of now, it has a very good retopology feature in the form of DynaMesh just as I described above. You just might have to do little adjustments when it comes time to animate your model back in 3DS Max or something to fit your needs.
Photoshop - one of the most universally useful programs in the world lol! Useful for creating your own textures, changing them, resizing, whatever.
Learn to Sketch/Draw in Real Life - this was probably one of the most important things that I missed back when I was starting. I thought I can do anything I wanted in 3D, but then realized I still needed to know how to actually draw! The reason? How can you create something in 3D without even knowing how to imagine and put it on paper in detail? 3D modeling isn’t just about copying something from a picture, sometimes you won’t have pictures to copy from and you’ll need a “reference” so you won’t forget what you’re trying to make. In situations like this, the best reference is inside your mind, but unfortunately not everyone is a genius so you’ll most likely forget how it looks in your head. This is where the importance of having the ability to draw comes in. The most basic you need is to learn how to draw objects from the front and side views (you’ll use these as reference in your 3D Modeling program, the idea is similar to “connect the dots” except you’ll also move edges and entire faces). By studying art and drawing, you’ll also develop the ability to “Think In 3D”, which is very important. It might seem boring trying to draw anatomy, humans, animals, and whatever, but you’ll suddenly experience the usefulness of such knowledge when making detailed models becomes a little natural to you and you actually know why you’re supposed to put muscles in such places and the like.
Learn Effective Topology/Retopology - basically, what a good “topology” means is that your model will be a lot easier to animate later on. For more detail, you better check out training material, books, and even free online articles as to why it’s important to think about the topology of your models.
If your parents still have some leftover cash after buying you some training videos and books, you might want to also buy a camera. It’s very useful to have a camera so you can just take pictures of, for example soil or trees, and then put them in Photoshop to transform into textures that your models can use.
Last piece of advice → 3D Modeling will really seem complicated and hard at first. This is especially true to people who has no prior experience with this sort of activity. Learn some art/drawing skills while you’re learning how to control your 3D Modeling program, it’s really important to have a background in drawing if you want to put your ideas in 3D form. Don’t get discouraged if you fail a lot of times, 3D Modeling isn’t something you can just learn in a month or so. The important thing is you’re getting the idea of how 3D Modeling actually happens. You’ll need constant practice. You’ll also need to remember that these programs get updated every couple months or every year, so an effective modeling method you know now might be obsolete later when a better method arrives (which is good for you). This is why it’s important to try to keep up with what’s the latest with your choice of software, it’ll help a lot!
Don’t get discouraged, just keep learning!
I’m pretty sure other more experienced people than me will have better advice, but I hope my tips would be of some worth to you 