A collapse in Centurion on Saturday saw the tourists bowled out in their second innings for 131, giving South Africa victory by an innings and 220, as well as a 1-0 lead in the Test series.
The West Indies failed to have a single partnership over 50 in the second innings, with Dale Steyn their main tormentor with 6-34 from 8.2 overs.
With the second Test due to begin on Boxing Day, Ramdin expects to see an improvement if the side are to stay in the three-match series.
"In our batting, we showed signs of batting partnerships but did not carry on at all," he said.
"They [South Africa] are a fantastic team, it needs a lot of character and we hope we can put a fight and challenge them.
"The guys were getting starts but we didn't carry on, we need to work on getting those big partnerships."
The West Indies will go into the second Test without main strike-bowler Kemar Roach due to an ankle injury. The 26-year-old did not bat in either innings after suffering the problem on day one.
For the hosts, captain Hashim Amla praised the impact of Steyn, who put the cramps that forced him off the field towards the end of day three behind him to produce a match-winning display.
"I didn't expect seven wickets in a session," he said. "We saw the wicket was getting a bit difficult to bat on.
"It was exceptional bowling from Dale that started the tumble.
"He did say it was cramps [that forced him off on day three]. He went away overnight, carbo-loaded a little bit and came back strong.
"I don't think many people appreciate how difficult it is to be a bowler in this format. We saw it was exceptional bowling, any team would have found it difficult to handle Dale and Vern [Philander] this morning."