General rules of car modding:

Never raise or lower your vehicle more than an inch. More than this (without modifying suspension geometry) tends to make the car handle very poorly & can make the vehicle unstable. The goal should always be to improve handling. Get an eibach pro or tein coilover kit or something like that. Lowering the car an inch with stiffer springs will make a big difference in the way the car looks & handles, but it will still be fairly streetable.

Lighter wheels are better. Every pound of unsprung & rotational weight that you can drop will have a many times the positive impact on the car as any other weight you drop.

Suspension bushings (upgraded to urethane & appropriately lubricated) often matter more than people realize, particularly if stock bushings are worn out. Other than the time & effort involved, there aren't any real drawbacks. Urethane engine mounts also have some benefits, but will increase engine vibration felt inside the car.

The most power for the least money is generally achieved by adding boost. Upgrade the fuel system & fuel management first (not exactly a simple or inexpensive task). Then look for an appropriately sized ballbearing turbo from garret or turbonetics. Doubling your horsepower will generally be more than you know what to do with. Don't buy a turbo thinking you will one day make 800hp. You can't grow into it, you won't make any power if you do this. "Area under the curve" or power across a majority of the rpm range is what you really want.

Buying a kit may be the better way to go, but in any case, shorter intercooler piping with fewer bends is generally better. Many short intercooler rows are better than fewer long rows. Bends & cooling channels are resistance. Similar ideas apply to turbo manifolds & wastgate ports. Smoother bends are better. Sometimes you will see wastegate ports turned in the opposite direction of airflow, you do not want that.

Improved engine cooling is something to think about too. But aside from rotary vehicles it's usually pretty straight forward & less of an issue these days. Air flow through the radiator is generally best when the air dam is ~1/3 the size of the radiator, & air can exit the engine bay from many places, but can mostly only enter the engine bay through the radiator (and intercooler). Ideally the engine would be fed cool air via it's own duct, not via some hole that will reduce the pressure differential you want to create between the front & rear of the radiator.

When you improve power it's important to improve stopping power too, however this can often be achieved with just a decent set of hawk brake pads & some improved brake cooling.

Reducing weight always helps, but don't lose sight of what you need to enjoy being in the car.

Engine internals (maybe with the exception of a mild cam) are generally the most costly (both in dollars & reliability) for the least benefit.

The more you mod a daily driver, the more unreliable it is likely to be.

Youtube is an endless wealth of car knowledge, but there are also a lot of tards out there too.