Lovecraft was a voracious reader but rarely did anything, or went anywhere (and I do mean anything or anywhere). He lived his life in reading books, writing his letters, and in between his own ears. Most of his close personal friendships were amateur/semi professional writers like himself, who he spent most of his waking hours writing to.
His family was "genteel" but had little or no money, leaving H.P. to think himself a gentleman, above work and above taking money for his writing. He loved finery and yet sabotaged himself at almost every turn along the way to being a successful writer. Almost everything he wrote was in amateur publication and his work would have been in the dustbin of history had not several of his long-time friends not pitched in to put together a Lovecraft anthology at his death.
Note: I wouldn't say that the elder beings were NOT technologically advanced, most of them used magic/godlike ability or slave races to accomplish amazing feats of building. I think only the fungi from Yugoth were considered a technologically gifted race. Races like the Elder Things used Shoggoths as slaves to build the city at "the mountains of madness".
Finally, while I recommend reading the works of Lovecraft, be prepared for wildly varying quality of literature. Some of it is amazingly imaginative and very unsettling, but some is so stilted and the dialog so affected that it is truly painful to read. Dialog for H.P. was hard, I suspect he had so little experience actually talking to anyone he didn't know how to write it.
He travelled a fair amount given his money and the time. He visited as far as Florida and New Orleans south and Montreal north, and wrote about them (including a strange travel guide to Montreal written entirely in character from the perspective of an 18th century English gentleman).
He conversed with people from a much wider area of course, via letter. But in an era when a major portion of Americans didn't own cars, and there was no interstate system, it's not bad. He of course lived in New York for several years, having a rough time (failed job hunts, all of clothes were stolen), and marking a period of his life of virulent racism that eventually subsided, as can be seen in both his letters and fiction.
As for influences, the man was a teetotaller, and stayed away from drugs, didn't even drink alcohol. While extremely well read and knowledgeable about the topics that interested him (astronomy, Classical Rome), he had little practical knowledge of the world despite every good reason that he should have. For example, several of his literary friends, who he visited in New York, were gay but it wasn't until well into his adult life that Lovecraft even knew homosexuality existed. He was amiable and clearly charismatic in certain respects (he did form a formidable circle of friends around him), and had a self-deprecating sense of humor, but he was in many ways a fairly extreme example of what we would today call a nerd.
Lovecraft's father was not a major influence in his life. Instead, the great positive influence in his life is his grandfather, who instilled in him a great love of history, antiquity, and myth. Probably the second most positive influence on Lovecraft was his wife Sonia. During the years they were together, she clearly worked to open him up, and he realized it and appreciated it. Unfortunately, he had been raised by suffocating aunts, and eventually he returned to that environment in Providence and retreated into a modified form of childhood.
This was the period when he wrote the works he is most famous for, his cosmic horror that moved away from the occult. He was a very strong skeptic of Houdini, in the sense we would use skeptic today. He was proud of collaborating with Houdini on a story, and according to Lovecraft in his letters, and I believe him though he may have interpreted these plans as more solid than Houdini did, there were plans for Lovecraft to co-author a book and expose of the occult with Houdini, the greatest debunker of his day, plans that were cut short by Houdini's death.
As for Theosophy, Lovecraft was initially somewhat aware of it when a fellow weird fiction writer brought it to his attention more fully. Lovecraft thought it was utter bunk, but loved it as material for his stories.
