How about a 147 for a start? The costs would be exponentially lower and it still has the good Alfa vibe. Starting with a 159 as your first car can get you easily out of wallet and love for the Alfa Romeos.
Let's look into practical stuff:
Insurance costs are going to be quite high unless you do the shared driving w/ your dad and you get the no claim bonus.
If the car is out of warranty you might incur into MASSIVE costs
Unless you have smaller rims, anything 18'' and above will be a costly tire to change
Road tax is quite expensive, do you really need a big boot and rear seats?
I've been there myself, I stretched myself beyond my means at first and it can be really frustrating, because there's so much you want to do to the car when it works, let alone when it breaks down! Mind you, it's nothing like it used to be, but the weak electrics/electronics,DPF/DMF issues on diesel models make it for a bumpy ride when owning a high end Alfa.
As I said in the beginning, give a thought to a 147, it won't disappoint you and it'll give you more time to look into getting a cheaper 159, think of it as a transition stage.