The Ley-Line Walker is one of the two Occupations in Rifts, along with the Shifter, that map most closely to the standard Wizard archetype of magic-user. (The Shifter gets his attention spotlight next week.) For reasons that I am uncertain (as of this post) that I comprehend, Palladium Books decided to split that archetype into two components. Whereas the Shifter focuses on the ritual summoning and binding of entities (natural and otherwise), with more utilitarian spell-casting as a necessary sideline capacity, the Ley-Line Walker flips this competence emphasis and then adds a few related toys.
The Ley-Line Walker, therefore, is one of the Occupations where the magic-user's origins are irrelevant because this Occupation is one of those whose power over magic is a product of years of formal study and practice- specifically, in the form of practical empirical experimentation and reporting of the results. As with the Shifter, the Ley-Line Walker is an outsider to the supernatural community, and only taken seriously due to the powers that they can command as a result of their research and development of magic technology--what we call "spells" and "rituals"--that they apply practically to the world. They are scholars and scientists that specialize in the paranormal, and nothing more.
The powers that this Occupation has with regard to ley-lines is what distinguishes it from others in the same archetypical category. Those powers are also shared by all True Atlanteans, so it is reasonable to presume that this Occupation arose with True Atlanteans long ago when they dominated Rifts Earth in its previous high-mana phase, and therefore non-Atlanteans who practice this Occupation can be presumed to benefit from some form of contact with True Atlantean culture. Furthermore, it is reasonable to presume that students learn to cast spells and conduct rituals as an outgrowth of mastering the ley-line powers; their entire paradigm behind the study and use of magic will be seen through that lens.
I noted previously that this Occupation is a prime candidate for people who want to be like Gandalf. Given that True Atlanteans, outside of whatever refuges they foster, are routinely on the move this should not be surprising; as they are, as a people, engaged in a resistance movement (complete with turncoats) against Lord Splynn (and getting caught up in others' struggles wherever they go in the process), it should not be surprising that they would want to foster their culture amongst friendly peoples whom they encounter- and this goes doubly-so for their fellow Men back on Earth. As a Game Master such NPCs are really easy to do; as a player, a Ley-Line Walker is the go-to option for when you can't play every session or you want an easy-to-insert character wherever your real-life interests take you.
This too should reflect itself in the Occupation's culture. While there are centers of refuge, of knowledge, and so on where Ley-Line Walkers (especially those too young, old, otherwise incapable) I would expect Ley-Line Walkers to travel frequently far and wide. I would expect them to become people whose everyday life consists of maintaining and expanding social networks, one-to-one connections that they can call upon in times of need in return for favors done. It explains why this Occupation emphasizes spell-casting over ritual works; rituals, while doable, are far more of a thing one does when staying in a specific place for any length of time whereas spell-casting is very friendly to frequent and regular traveling. A Ley-Line Walker cannot help but to become a cosmopolitan, multi-lingual, broadly-traveled individual over his lifetime- much like the True Atlanteans that founded this Occupation ages ago.
So, think like someone who's always on the move. Travel light. Be self-sufficent. Be a good guest; you never know when those whom you meet today are those whom you call upon tomorrow. (Yes, even for evil characters this makes damn good sense; bridge-burning is bad for business.) Know the territory and those who dwell within it. Help when you can, how you can, those who need it (and, frankly, deserve it; again, evil would do this too). Be like Gandalf (or, at worst, Radaghast) and you'll do very well as a Ley-Line Walker indeed, and in so doing you'll hit what True Atlantean culture is in the cosmos of Rifts.