Hi! I was around 16 when I joined... k10's are the perfect first car. I drive a volvo 480 day to day now (also a great car) but k10's have a charm that imho cant be rivaled. Like the ultimate Lego set
Enjoy!
As for performance, its difficult to imagine the absolute enthusiasm you have when you get your first car/micra. I would start with a k&n filter. It doesn't really make any difference, but it feels like it does and sounds good
My favourite mod was the alternator cut off. A relay connected to the charge lead from the alternator. Flick a switch and there is no alternator drag on the engine. That does make a difference, but you need to be careful using it.
If you have the resources, consider a different exhaust manifold, cam and inlet manifold/carb setup as the first step.