What software should I use if I’m a beginner in 3D design?
The first thing I would do is ask myself this question "what do I want to accomplish with 3D software skills?".
If I want to design houses then find out what 3D software is used in the architectural industry (probably AutoCAD), if I want to design creatures for the movie industry find out what 3D software is used in that industry (perhaps Maya, I'm not sure), if I want to design products most companies in the industry will use either Creo Parametric (Pro/E), SolidWorks or AutoCAD Inventor.
Don't waste your time learning a software that won't apply to your end goals. It will only frustrate you when you discover it doesn't work the same way and you've developed habits that hinder learning the right software.
If the software is more than your budget try to find a job at a company that uses the software so you can gather some experience there. Or take classes that teach the software at a community college or adult learning center. Search for online tutorials as well. Any experience you can get using the software will put you on a path whereby you can earn the funds to purchase your own copy of the software.
Even the high end 3D CAD software like Creo Parametric, Unigraphics and SolidWorks offer student editions at a lower price. These versions usually don't have all the powerful features of the commercial versions but they are a generally useful regardless.
First set a goal, the goal will determine the path.
Good luck to you!