I would say the first step to begin would be to look for a GPS receiver.
It should really be RTK capable and dual band, a popular chip is the F9P.
For easy RTK use you should look for a free base station near to you (less that 100km). RTK2go stations
In some US states there are CORS ,free stations networks
If you have have a station near, you only need a GPS receiver (most used is Ardusimple simpleRTK2B) a windows tablet or laptop, an usb cable and a cell phone with data(to create a hotspot) to have RTK precision.
With this you can get familiar in real operation and upgrade later with autosteer.