Chris Hughton snapped up the attacking midfielder for just £3m after the former Germany youth international impressed in the Bundesliga.
Gross scored five times for FC Ingolstadt in the 2016–17 season as they were relegated from the German top tier. But the chances he consistently created is what really attracted Albion.
Despite playing for a struggling team, Gross teed-up an impressive 95 goal scoring opportunities - more than than any other player in the league that season.
The former Karlsruher and Hoffenhiem man adapted to the Premier League with minimal fuss and quickly became a trusted and top performer for Hughton.
He agreed an initial four-year contract but his arrival was somewhat overshadowed by the likes of expensive signings Jose Izquierdo, Davy Propper and Maty Ryan as Brighton bolstered their squad following promotion from the Championship.
Even left back Markus Suttner, who also joined from Ingolstadt that summer, was more expensive at just over £4m.
"Brighton were very active," said Gross earlier this season. "At the first conversation they showed me the scouting report they had gathered on me.
"The 40 to 50 page scouting report on me was really impressive. It contained everything about my private life, and every game, strengths and weaknesses.
"They knew everything, were present at almost every match live. In the report, I found myself again and said, 'Yes, that's how I see it too.'
"There was a huge interest from the club and the coach (Hughton). Which is always the most important thing for me. The responsible people made a great effort for me."
Anything in the comprehensive dossier he didn't like? "There are always little things, but by and large, I recognised myself in the report, and found them to be top-professionals." added the German.
"I was here looking at the training centre, the stadium, and the city. I thought twice or three times because it was a big step for me.
"In the end, I was very convinced, they gave me a good feeling. So I said to myself: I'm trying the step into the Premier League."
Gross immediately secured his place in Albion history by scoring Brighton's first ever Premier League goal in a 3-1 win against West Brom. He also added a second and claimed an assist for Tomer Hemed.
It was soon clear Albion had made a shrewd piece of business.
He concluded his debut season in the Premier League with seven goals and eight assists and was comfortably voted the player of the season at the Amex.
His performances didn't go unnoticed and at one point Liverpool were said to be keen. Gross said at the time, "It's an honour to be linked but I have not heard anything concrete.” He was swiftly rewarded with a new contract with Albion until 2022.
Gross said, "I heard nothing of it myself (Liverpool interest), and only received the article from friends. But actually there was nothing in it. There have always been requests from lower clubs, but that was not an issue for me at the time.
"There were one or two things from Germany. After my first year, I definitely did not want to go away, and I wanted to continue to play in the Premier League, that's what I told my agent. "
The second campaign was solid rather than spectacular as progress was hindered by niggling injuries. He did however play a key role in helping Albion maintain their top flight status with a vital goal to earn a point against Newcastle.
Hughton left and Graham Potter arrived but Gross remained a reliable figure for the new manager. Gross is not blessed with blistering pace but his delivery from wide areas and set pieces makes him crucial to Brighton's style of play.
Potter likes to play good football but set pieces are also key, especially with giants in the team such as Lewis Dunk, Adam Webster, Shane Duffy, Dan Burn and Glenn Murray. They have all benefited from Gross' accuracy with the dead ball.
Gross has previously said he'd love to finish his career in Germany but he is still eager to achieve more in the English top flight and make the most of his time with Albion.
"Brighton is a big club because they play in the Premier League, but they're also very modern in England, with a new training centre and a new stadium." said Gross.
"The club is also family oriented and at the heart of the club is owner Tony Bloom, who comes from Brighton. He loves the club and wants to bring them forward."
Few players in the Premier have offered such value for money and the 50 page scouting report proved correct.
What they saw at lowly FC Ingolstadt has been recreated in the Premier League for £3m. Give that scout a bonus!