Windows 7: What would be the best for me?

Hello all!
Yeah, I have saved up a little and could afford some upgrades for my computer again but this time, I'm not sure what should I get with limited budget of SGD$80 = around USD$50.
So, I would like some advice since I'm not sure what to upgrade this time. XD

Over at my country, I can afford the following;
- Another stick of 4 GB RAM. ~ I already have 2 x 2 GB of RAM. If I were to buy a 4 GB RAM, I have a spare 2 GB of RAM hanging around.

- WD 800 GB HDD, Green one. ~ Not sure what does their colors meant but all my HDD are from Green.



- A random graphics card, I guess. ~ I know nothing of graphics card but I know that my current graphics card isn't good. XD

- A router to make my house wireless. ~ Would be cool to go with my iPod/iPhone.

- A portable HDD. Looking for at least, 320 GB and above. ~ Should be quite useful at times but I wouldn't be sticking it into my computer daily.

Any advice would be good. MUCH THANKS!!!

1. extra RAM will buy you a little performance, but not a lot
2. an extra HDD is useful if you have a lot of data and for a little performance gain when you move large amounts of data around
3. a graphics card may make sense if you play games - for normal use with pictures and videos it will not buy you a lot
4. a router is nice to have, but unless you have several PCs spread over the house it makes limited sense. It does, however, increase your security because of the built in firewall
5. an external disc is always useful for offloading data and for imaging. And it is pretty safe from malware when it is not always connected. That would be my first choice.

I'd get the wireless router because almost every device you buy now wants to connect to the net.

Thank you, whs &z3r010 for the suggestions.

I know that a portable HDD would be good and it'll be real handy to me at work and I'm thinking of choosing a good one since I only like WD ones. XD
Yeah, sir, most of my devices needs the net and well, it's really hard to choose from them all and I got limited budget. =C