I have a scion Tc and i want to upgrade the audio bymyself any do you have tips or have any of you done it?

what kind of speakers are good i dont want to spend alot of money on this. i am very good with audio and sound stuff i also know quite abit about cars so that wont be a problem. if you have done it what speakers did you use like amps, recievers, subs things like that and even if you didnt do it yourself what did you use if you had someone else do it. any help is appreciated. real answers only please.