Down here in Texas there are a ton of good shops.
Check your tint laws and stay legal.
In NY, the law was 70 percent I think, which basically means no tint on any windows that has seating for passengers.
Down here we are 30 or 35 percent on the front windows, the rest can be as dark as you want.
I would NOT do it myself, it will not come out good unless you know what you are doing.
I had two cars done with entry level 3m brand film, and they are perfect.
The shop that does mine has a plotter cutter that cuts perfectly shaped pieces for the window that is unique to each car.
I did 35 percent all around in my car, and I wish I would have gone darker in the back of the car. It is not dark enough in the 100 degree heat.
The good branded tint, 3m, LLumar does not turn purple or bubble and you get a warranty if it does.