My tips:
1. Save money by choosing a 'free' colour. Choose white if you want to confuse some dimwits that you are the police, or if you want to find your car easily in a carpark!
2. 18" wheels are a must, but they're a 1000 quid option on the GTI, so 'save' (

) money by ordering an Edition 30, where they come as standard (pescaras not monzas,but very classy)
3. If you use the car in early starts during the winter, don't get the 'winter pack', but instead order the Edition 30, where heated seats come as standard! (Yet more savings...erm)
4. Xenons: an expensive option, but having now used them in anger in unlit country roads, the difference in visibility is so great that driving is simply less stressful, and you get other benefits like self levelling and the ability to adjust them for the continent without silly fiddly bits of sticker being slapped on the headlight plastic. I genuinely think these things add to the safety of the car, so surely that's a no brainer of an argument for getting girlfriend buy-in!
5. Multifunction Steering wheel: not necessary unless you need to use handsfree phone all day in the car. If you order DSG, you don't need this option to get the flappy paddles, as they come as standard.
6. DSG - the normal gearbox is great, but many of us have plumped for this DSG thingy and it makes a huge difference to the experience, but if you're looking for must-have options, I don't think not having DSG will result in your car being able to sell at a later date. It's worth having a go in one though - the dual clutches make for amazing gearchanges that you can either control yourself or leave it in auto mode.
7. Leather seats - Again, the Edition 30 saves you more money, as the seats are part leather, part cool GTI check, which looks better than full leather in my opinion, yet is included in the price rather than being an eye wateringly expensive extra (which the full leather is)
8. Many people chip their GTI. Save money by avoiding this step (for a bit at least) by getting an Edition 30, which is a bit nippier than the GTI in the first place but with a similar fuel economy.
In short, the edition 30 saves you money!
(erm

)