I recommend DraftSight because it is free, and even its paid version is much cheaper than AutoCAD. Still, it has all the features you expect from a CAD.

Another advantage is that you can install tools (plugins).

Well, as you have already heard about your question, let me explain the answer.

There are many options for 2D and 3D software on the market. If you study engineering and want to specialize in mechanics, SolidWorks can be interesting because you can, from the 3D model, study the structure of the part with SolidWorks simulation.

If you also want to learn 2D software, I recommend DraftSight, a free CAD software, where your paid version is much cheaper than the other models on the market. Yet, it has all the capabilities of CAD and applications to incorporate.