I use Elixir strings on my steel string acoustic guitar. I’m very happy with them as they have a crisp sound and last a long time. I make sure to wipe them down with a soft silver polishing cloth every time I play and change them about every 6 months.
I have been using these D’Addario nylon strings. I like the tone, and I change them about every 6 months as well. They make several different sizes, you’ll have to experiment and see what you like best.
Most all the strings they make now are very good. I use Ernie Ball strings on my electric guitar.