Get yourself a decent RAM: 4GB is enough
A fast processor: everything above 2.5GHz will do (double/quad-core won't matter)
A nice Gfx-Card: On older cards I tend to advise ATI the 3850/4850 for example worked like a charm, when you are heading for newer cards, then get yourself a GTX260 from Nvidia which has no problems with FH2.
And if you have some money left over get yourself a decent and fast Harddisk and that was it.
Now that above was all for a budget PC.
If you have the cash, just buy any new PC with 4GB and it will be able to run everything at max.
(I believe your Dad can help you there, seeing how its your birthday.
)