I personally would say a 2003 - 2004 Yaris. I have owned mine for nearly 6 years and its served me well. cheap 1ltr engine, cheap road tax, insurance and steady on the petrol. Easy to manage. Not very strong but works well under normal usage. Driving with a full set of passangers can feel different but other than that I have been happy with mine.
I think loooads of people will say get this get that but really its all down to you and you will learn your own way what feels right and what doesnt.
if its your first car and your under 21 I would suggest something like a yaris or any 1ltr engine bubble car. Just check the history thoroughly look out for re-occuring faults, go private and make sure its from a normal working family or pensioners that want to get rid. dont get it from some dude that has ragged it around communities or motorways etc.
and have a little test drive in it too.