gmodels::ci() calculates confidence intervals for model estimates, and I believe you want to estimate a confidence interval for the population mean, so you can try using something like this.
df <- data.frame(stringsAsFactors=FALSE,
Name = c("Sudira", "Suas", "Sumi", "Suresh", "Rakesh", "Ravi",
"Roshan", "Raghu", "Srikanth", "Guru|"),
Age = c(23, 28, 26, 29, 53, 22, 30, 27, 35, 23)
)
t.test(df$Age, conf.level = 0.95)$"conf.int"
#> [1] 23.09414 36.10586
#> attr(,"conf.level")
#> [1] 0.95
Created on 2019-08-06 by the reprex package (v0.3.0.9000)