Johnson has already roped in midfielder Carl Winchester from League Two outfit Forest Green Rovers and could further bolster his squad with the winter window open.
The Black Cats boss is overseeing his first transfer window at the helm of the Stadium of Light and has identified key areas that need strengthening this month.
But Johnson revealed that his side are being extra vigilant on how to conduct their business as Sunderland have suffered from making snap decisions in the market too many times in the past.
Asked about further transfers in the ongoing transfer window, Johnson told a press conference: “Not an awful lot [is happening] to be honest with you.
“We need to get the value.
“Too many times in the past this club has chased it, made snap decisions and got it wrong.
“We’re being vigilant to make sure if we do it, we do it right.”
Johnson also backed new boy Winchester to shine in Sunderland colours as he stressed people will be surprised at how good a player he is, having already coached him at former club Oldham Athletic.
“I think people will be surprised at how good a player he is
“He brings an assured quality on the ball.
“He’s versatile, he can dictate when you’re in control and he can hustle when you need him higher up.”
Johnson could opt to hand Winchester his debut when his team travel to Plough Lane at the weekend to take on Wimbledon in their upcoming League One clash.