"The best" is elusive. What model / size guitar do you have? Do you intend to use or depend on mics at all, or are you looking to avoid stage mics? Do you have high stage volume to contend with, or do you do solo stuff? Concert or Tuesday night bar scene?
Each of these will affect what works for a system, and part of the system will be the guitar. Are you really prepared to engineer this?
In general, multiple stage mics will produce the best overall sound. They are holy terrors to contend with, though, particularly if you tend to move. Don't have a stool? Then keep looking.
Next on the list is likely to be one of many undersaddle transducers. Biggest benefit is their tendency to allow gain before feedback. Their downside is a characteristic "piezo quack" or unnatural sound.
Best overall may be a combination of an undersaddle pickup (piezo or electret) and an internal condenser mic. Both systems will require a preamp of some kind. Look at Baggs, Fishman and the like for a representative sample.
Everyone seems to think you can do this on the kitchen table yourself, like painting the back of the house. Not quite as easy, and simple to mess it up. This is rather difficult to do WELL, and that will affect the sound.
You can spend $200 - 500 in a New York Minute with aftermarket installation, which is why it may be more cost effective to consider trading the instrument in for one with onboard electronics.