Speaking to reporters on Tuesday, Ricken said Dortmund's priority had been keeping the core of last season's squad together before looking to strengthen in key areas.
"The core of the team has stayed together," he said.
"It has often been written that Schlotterbeck is leaving, and Guirassy and Nmecha and Ryerson – no, they're all still here. And I think that's extremely important."
While pleased to have retained several leading players, Ricken made it clear Dortmund's recruitment drive is not over.
"Of course, we're not satisfied with that. We want to make another one, two or three really good signings," he said.
"But we want to make the right transfers and not just any transfers that earn us short-term applause and then in November we suddenly have the problem of asking whether they were really the right transfers. We are taking our time to sign players who ultimately make us better."
Borussia Dortmund have already been linked with a number of attacking players during the current window, including Genk youngster Konstantinos Karetsas, Hoffenheim forward Fisnik Asllani, FC Köln prospect Said El Mala, Club Brugge striker Nicolò Tresoldi and Paris Saint-Germain forward Randal Kolo Muani.
Ricken also highlighted the work already completed behind the scenes, pointing to several young additions and the progress of academy players.
"We've already brought in three players with Joane Gadou, Kauã Prates and Justin Lerma. Gadou has really strengthened us in central defence, and with players like Reggiani and Inácio, they're effectively new signings as well. We didn't necessarily expect them to be this far along already and capable of making a sporting contribution."
The former Dortmund striker also challenged several of last summer's arrivals to make a greater impact this season.
"We have players we signed last summer, with Silva, Chukwuemeka and Bellingham. I think they will improve, and that's our expectation as well, that they take the next step."
Dortmund remain active in the market, but Ricken's message was clear: quality will take precedence over speed as the Bundesliga club continues its summer rebuild.