Having problems with my 98 Ford Escort?

98 Ford Escort - Ok I Have Been Having A Idle And Jerking Problem. I Guess The People That Gave Me The Car Told Me That The O2 Censers Are Going Bad And The Cables And Clamps To The Battery Are Bad But Im Not Sure If It Is That That Is The Problem Or It Could. When I Star The Car It Idles Between 500rpms To 1000rpms When I Put It Into Drive It Idles At 500rpm Sometimes It Has Quit On Me. And When I Drive Around 40mph It Drops Down I Rpms And Start To Jerk I Let Off The Gas And Hit It Again And It Drops Again And Jerks Again Repeatably And When I Hit The Breaks It Raddles Down Like It Vibrates The Car Can Someone Help Thxs