Your calls to plot() and lines() do not have any x values. Notice that in my code I passed both the Date and the Auto column to plot(). Try this.
library(lubridate)
data1$Date <- dmy(data1$Date)
plot<- plot(data1$Date, data1$Auto,type = "l",col = "red", xlab = "Date", ylab = "NIFTY point", ylim = c(0,35000), lwd=3,
main = "NIFTY indices of different sector")
lines(data1$Date, data1$Bank, type = "l", col = "maroon", lwd=3)
lines(data1$Date, data1$Financial.Services, type = "l", col = "green", lwd=3)
lines(data1$Date, data1$FMCG, type = "l", col = "dark green", lwd=3)
lines(data1$Date, data1$IT, type = "l", col = "purple", lwd=3)
lines(data1$Date, data1$Media, type = "l", col = "yellow", lwd=3)
lines(data1$Date, data1$Metal, type = "l", col = "magenta", lwd=3)
lines(data1$Date, data1$Pharma, type = "l", col = "orange", lwd=3)
lines(data1$Date, data1$Private.Bank, type = "l", col = "cyan", lwd=3)
lines(data1$Date, data1$PSU.Bank, type = "l", col = "black", lwd=3)
lines(data1$Date, data1$Reality, type = "l", col = "blue", lwd=3)