Some popular standards to try are D'addario EJ45, La Bella 2001 (I prefer medium hard tension), Augustine (perhaps try red or blue imperial), Savarez New Cristal. These options I think will give you a good sense of the spectrum of strings. You may want to give Carbon trebles a try such as Oasis GPX... carbon trebles are known for being more responsive, sustaining, and with higher volume, but may not have as much complexity than nylon. Leave strings on for at least 2 weeks to hear their true sound potential.
Another absolute essential is knowing how to shape and polish your nails along with proper right hand technique as it makes a world of a difference.
"Success grants its rewards to a few, but is the dream of the multitudes.
Excellence is available to all, but is accepted only by a few." - Christopher Parkening