The team have experienced a number of changes in recent weeks, with Buttler assuming captaincy from Eoin Morgan and Matthew Mott arriving as the new head coach.
With international games coming thick and fast, the new skipper didn't have much time to find his feet.
However, despite early defeats against India, the England skipper is now on the precipice of leading his side to victory over the Proteas.
England won the opening T20 match of the series with a 41-run victory in Bristol. South Africa levelled the score by securing a 58-run win in Cardiff just 24 hours later.
Speaking ahead of the series decider, Buttler said: "You want to win every series that you play and we haven't won a series yet this summer. That's something we're not accustomed to as a group.
"But this is a start of a new cycle of a team. There's been a few changes - a new captain and a coach (Matthew Mott), and I feel like that's showing a little bit. We're still working ourselves out and gelling as a group and we need to do that quickly. Winning this series would be great for that."
South Africa's match-winning score on Thursday was built around a knock of 96 not out from Rilee Rossouw, who put his international career on ice for six years with a Kolpak deal at Hampshire before his return to the fray this week.
"That was special," he said at the close.
"Representing your country is the proudest thing anyone can do and today was emotional for me. I'm grateful for where I am right now, to put in a performance like that for my country is special for me. Hopefully there's a few more to come."