Anyone can buy a Masonic ring, anytime. I bought a cheap ring from a hock-shop, before I completed the MM degree. I wear my Grandfather's heirloom ring, on special occasions:
Grampaw's Ring
I bought a nice "everyday" ring, through an estate sale.
I live in Iraq, and I do not want to take a risk, on losing my good ring, so I bought a stainless-steel ring for $50.
There are a number of good rings for sale on E-bay.
You should not wear a masonic ring, until you have completed the Master Mason degree.