If the debate is whether to get the Eurocharged tune OR the Sprint Booster, you're much better off with the tune because it increases real horsepower and reduces some throttle lag, whereas the booster reduces the lag but does not actually give you any power. If you're up for buying both potentially, get the tune first and then see if you feel you still need the booster

As far as the rest of the mods go, Eurocharged can be the first thing you get because as you upgrade other parts, you will get free retunes so you'll always get the most of your upgrades (i.e. Changing to a better intake will bump your power some by increasing air flow but your car is "smart enough" to adjust closer to factory spec.. Getting a tune will "teach" your car to use the new air flow instead of "compensate" for it)

This advice is for anyone: if you think you'll eventually at some point in time get the Eurocharged tune, buy it now while its on sale as there is literally no down side to having it first