Getting started in DMR is simple. You need to hold a FCC amateur radio Technician level or higher license. Be in an area with a DMR repeater. Have a DMR capable radio. Request a DMR user ID.
I started with a low cost Tytera (TYT) MD-380 handheld radio that I purchased new from eBay for under $110.00 shipped. It was a great starter package that included the programming cable and software. With limited information I was able to get on the first area repeater within an hour of receiving my radio.