You say that you drive it a few times per week??
As you drive it, ask yourself what you like the least about driving it.
Lack of power? Start with an engine swap....
Poor handling? Start with suspension upgrades...
YOU are the only person that can give yourself a starting point as far as modifications/upgrades..
If you can't decide where to start, then drive it everyday for a couple of months, then you'll know where to start with upgrades..
