Arriving at beijing west rail station at 12pm. which train will travel to guangzhou lowest price?

Its first time to me to be in china and am going to find a spicific product in the city so i want to lower my travel expencies by taking the lowest train package with the harder seat so my Q is : which train can i talk on saturday 21-3 at 12 pm ?? And how much it will cost me ?
P.s i have my travel bags. Need an answer plz.