That depends on what you want to make. If you’re making simple shapes and text, a free 2D CAD software is probably easiest. If you’re making 3D brackets or moving assemblies, you’re going to spend a lot more time trying to figure it out in 2D, so 3D is the better choice. Most CAD software functions similarly (2D packages are similar, 3D parametric software are similar, etc), so if you invest a little time to learn whichever style of software you need, you’ll be able to transition between similar options fairly easily. Learn the basics first, and if more advanced CAD features can make designing your parts easier, learn those as you need them.