Hi - Welcome to the site.
You've started simple. Thats good! I don't think the titanium tax disc holder would have much impact on performance (unless it is paired to the stick on titanium petrol cap cover
) What engine do you have some are very tunable and others do not have much to give?
How much are you looking to spend and what sort of car do you want to end up with? Economical torquey hack? Road burning high revving flame spitting monster or something in between?