I started with Draftsight
It is a simple 2D software package that you can Download for Free.
Draftsight is limited in that it only works with DWG and DXF files.
I recently bought Turbocad Deluxe 2D / 3D. It can import and export files
in a Lot more formats.
I still have to teach myself how to Use Turbocad in a Productive manner.
There really is No way around that