The first mod I did that got the ball rolling was a really good set of performance tires. Toyo Versado CUV 225 55R18 98V to be exact on some decent rims.The tires instantly revealed the old/weak suspension. I can easily out drive the suspension(not a good thing) you can get into a lot of trouble really quick (roll overs and other miss haps)
I am currently working on the suspension. There is some really good product available but they take a long timeeeeeeeee to get (addco sway bar, koni 3way adjustable shocks/struts, poly kits were 5 months from order to delivery). I'm doing a conservative drop of only .5" so the geometry stays very close to OEM, later I might do a 1.5" but I want to see how the first setup handles.
I'm half way to rear LSD.
The last thing I will look at is more power. Its tempting to do it sooner as I just got a chance to drive a very well setup rav4 with a 3sgte swap but I'm sticking with my plan (I have to keep telling myself this) lol