This Traverse may the poorest take Without oppress of Toll—
Books may cost money, but reading them is free. So, anyone with access to books (like, say, through local library or Project Gutenberg) is able to travel in these magical bookmobiles along the superhighways of the imagination.
The speaker expresses this simple idea by saying that even the poorest person can take this kind of "Traverse," or journey, without ever being "oppressed" by having to stop at a tollbooth and pay.
How frugal is the Chariot That bears the Human soul.
"Frugal" isn't a word we use that often anymore, since most of you probably don't remember the old-school Eighties cooking show The Frugal Gourmet. Basically, it just means "inexpensive," or "affordable."
Similarly, we don't go around bragging about our new "Chariots" to our friends – instead, we call them "cars." (Well, technically, a chariot is drawn by a horse, but you get the point.) So, just replace these old-fashioned words, and the meaning of these lines becomes clearer right away: dude, the car that can carry the human soul around is dirt cheap!
The speaker here expresses wonder at the fact that reading can carry your "soul" or imagination on a kind of joyride, and it's totally, one hundred percent free.