If you are only 14, then you need to ask your parents for a laptop/desktop. But it's best if you simply ask for a Xbox 360.
Over time computer games are designed to be more demanding because new hardware are released on a more or less regular basis. Consoles never changes it's internal hardware so a 2013 Xbox 360 game played on an Xbox 360 bought back in 2009 will run just as well on an Xbox 360 bought this year. The same cannot be said of PC games.
However, the next generation Xbox and PS are expected to be released later this year.