It all depends on what u wanna do with the computer and also thinkin' abt the future..! If it is just for internet use and doing other normal things, then u can find many cheap pc's..! But if u r doin' any programming stuff or loading or running huge servers or other programs, u need to do a bit of research and buy what u want..!
Sometimes, they sell cheap pc's at normal stores like
LIDL,
Aldi,etc...so u gotta check that..!
Also,check for "Dell" offers...Their pc's are good and reliable..! U can just call them and ask for options and also make them configure what u want and what not in ur pc and they will take some weeks time and deliver that to u..! The best part of dell is its reliability, good technology and also the technical support they provide..!