It is the perfect ruse.
Firstly, it benefits him. In order to move out of the Orphanage after he had turned seventeen had required a job, and he had created an opening at Borgin and Burkes. There had been little competition for the position when the details surrounding the sudden disappearance and grisly death of the previous employee had been made known in the right circles.
Secondly, he finds the work interesting. Some of the under the counter deals he did with some of the more disreputable customers were truly fascinating and enjoyable. Sourcing rare and illegal ingredients from closed countries and smuggling them in right under the nose of ministry employees was exhilarating. Sifting through secret libraries of banned tomes for long forgotten dark magic rituals, curses and spells was illuminating and gave him a few rather brilliant ideas.
It is also his job to relieve witches and wizards of their expensive and eclectic heirlooms, work he found himself well suited to. He became well versed in persuasive tactics, knowing when to use threats and violence, and when a charming countenance was required.
Of course, the most useful aspect of his employment was the customers. They were on the wrong side of the law, seeking to get rid of an illicit item for a bit of coin, searching for a rare and expensive item for an illegal potion, or occasionally searching for the perfect cursed accessory for their cheating husband. They were his people, and it was from the unsavoury types that walked through the door that he recruited his followers.
Tom Riddle had always known he was destined for greatness. Long before that fool Dumbledore and walked into the Orphanage and told him he was special, he had honed his taste for power and cruelty, harnessing the urges inside him to influence the world around him to his tastes. The other orphans had been terrified of him, refusing to meet his gaze or stay in the same room as him. He had given them good reasons for their fear, which he had seen as the respect he deserved.
Entering Hogwarts had opened up many opportunities for him, and over the years he had nurtured his ambitions, learning all he could and drinking in every facet of the wizarding world. The purebloods had fascinated him, his fellow Slytherins. They had the right idea about the world; putting muggles in their rightful place, using their cunning and sharp intelligence to propel them to the top, playing the emotions of others to their best advantage. He had made himself one of them, fashioned himself in their image, and, eventually, became more them then.
Within the first few years, he had established himself as a leader. His students deferred to him, recognising his great intellect and the wellspring of powerful magic he had contained inside of him. He was a powerful wizard, and they all knew it.
Since finishing school, he had been laying the groundwork for his plans of greatness. What the wizarding world needed was a strong leader. Someone who wasn't afraid to do the dirty work of ridding the magical community of mudbloods and squibs, of getting rid of the threat of muggles by decimating their numbers, by achieving supremacy through any means necessary. He was that leader. He was a visionary.
His job at Borgin and Burkes allowed him to share that vision with his fellow man. To slowly gather loyal followers into his circle, to sway them and make them see what needed to be done.
As his influence grew, he began to attract some more powerful members of the magical community. He had known of the Malfoy family of course. Abraxas Malfoy was an important political figure in the wizarding world, and he had brought his son into Borgin and Burkes and introduced him to Tom. He was a rather promising young lad, Lucius, who was just starting his first year at Hogwarts.
Tom had taken a shine to the boy, who was full of his own self-importance, had more money than he could ever spend in several lifetimes, and was easily swayed. This one was to be groomed for his inner circle. Lucius had so much promise, and he would bring his peers with them. Tom needed young blood like them to fulfil his vision of greatness.
While Abraxas was doing business with the store owner, Tom took Lucius aside.
'So,' he began conversationally, 'you will no doubt be in Slytherin?'
'Of course,' Lucius responded, pride evident in his tone.
'I graduated as Head Boy last year, you know,' Tom informed him.
'Yes, father told me,' and his look was full of respect. Tom clapped him on the back, a technique he had learnt at Hogwarts to set a peer at ease.
'I hope you will in time consider me a friend,' Tom said, a more predatory look in his eyes now, though Lucius didn't seem to notice this. 'Anything you need, be it goods or advice, I will be here to help.'
'Really?' Lucius seemed sceptical. Already a Slytherin; he didn't trust the idea of giving something for nothing.
'Of course, one day you will repay the favour. I can be a useful ally,' Tom said with a cold smile, and Lucius met it with one of his own. There was a mischievous twinkle in his eyes now. Bargains and bartering he understood. Tit for tat. It was the Slytherin way.
Lucius nodded. They had an understanding.
As the boy left the store with his father, Tom felt a shiver of anticipation run down his spine. Something momentous had just happened. He had a feeling that he and Lucius would achieve great things together.
With a cruel smile, Tom donned his cloak and stepped into the back courtyard behind the store, reserved for apparition. It was generally used by customers who didn't wish to be seen entering the store, but Tom used it now for his own purposes.
He apparated, and found himself in front of the large, gaudy mansion of Hepzibah Smith.
Yes, all the threads are starting to come together.