It depends on the car - good modifiing is "fixing" the shortfalls of the car, ie if you have an ST220 and you drive it hard - the brakes are barely adequate braking from 150mph (off road, of course!) - plenty power - poor traction, so st225 brakes and an LSD are on the cards
But -
Most modern Fords have great handling, and you don't really need bigger wheels/ tyres (bigger wheels (eg 18s) dont make that much difference and are mostly for looks, same with lowering the car, often the handling is worse
So if you have a 1.4L or 1.6L Fiesta or Focus etc, the standard brakes, wheels, tyres,/ handling are probably more than up to the job,(if looked after/ serviced + decent tyres fitted) and all you really need is MORE POWER 
I agree about handling being decent along with the brakes. At the end of the day, I think it all depends on preference and how you drive your car.
More power I think is the best bang for your buck. Remap would put the biggest smile on your face as well.
My top 5 list:
1. Air filter. I am dubious of the efficacy of whole induction kits. Check out the Mighty Car Mods episode about that. Very educational. Cheapest option of getting a reusable air filter from K&N or Green Cotton will add a nice sound and make the car run better with a slightly improved fuel efficiency. So far have done that to 3 different cars: 2 Foci, 1 Renault Megane and 1 Seat Leon. Very happy with the results.
2. Wind deflectors. Quieter cabin on long motorway journeys. Not too expensive mod and the car looks nicer I think.
3. Sound system. Nothing beats a decent sound system while driving by yourself. Always puts a smile on my face when I crank the volume to a good tune.
4. Remap. Thinking maybe Superchips Bluefin for the ease of access and good reviews from what I have read.
5. Suspension. Shocks, springs ,anti roll bars and exhaust.
This is my current wishlist