This can be completed very easily. You only need to walk around and find whatever plorts you come across. These should easily total 50 within a day. However, if you'd like to be more efficient, I would suggest lumping this together with all of the "Sell --- plorts" and "Earn --- Newbucks" achievements. See my guides on those achievements if you'd like. Once you've finished the prep work that i describe in those guides, 50 in a day will be nothing.
Here's my video for every achievement if you'd prefer. Skip to 4:27 for Free Rangin'.
Happy Hunting!