Let me discuss a little bit my impressions and memories of the tennis string I've used so far, in general terms.
I've been playing tennis for almost as long as I can remember. I started out as a rather young kid, playing on a somewhat sandy tennis court, using someone else's rather heavy racket. So my first rackets were not mine. They were usually racquets belonging to members of my immediate family, or perhaps some of their friends who were kind enough to lend theirs to me for a while.
So in the beginning, I had no knowledge at all regarding tennis string options. I used other people's rackets, and I adapted to the said rackets, and these rackets' stringing. I only actually began to notice the effect of the gut on my game much, much later, when I bought my first tennis racket.
It was one of those tennis rackets which did not come already strung. In fact, it did not come with any string at all, which was a surprise to me. I learned then how to check a tennis racket for information on the recommended gauge and tension of the tennis gut to be used with it.
So I made my first purchases of tennis string. At the start, I would only use string of the same brand as the racket. I wanted them to match. I knew that the major tennis racket manufacturers that I was familiar with also sold tennis string, so at that point, I was only aware of string being sold by the likes of Wilson, Prince, and Head. It would only be later that I heard of other brands such as Babolat, Gamma, Luxilon and the like.
Thankfully, the shop where I bought my tennis racket also had matching tennis string, as well as someone on standby to do the actual stringing. So soon enough I left that store with my tennis racket complete.
Fast forward to today where choices abound. Many manufacturers of gut are out there, some familiar, some less so. One manufacturer can provide many different kinds of string, created from different materials (natural, synthetic, nylon, polyester, kevlar, and the like).
A tennis racket may have a recommended string gauge, but you can choose to deviate from it. Also, after some time has passed, and you've played quite a bit, you'll get a sense for what gauge in particular is right for your type of play. The same is true for the previous choices mentioned, as well as choices related to stringing, tension, and tennis string maintenance.
So now I have my favorite tennis racket, favorite string, and favored setup, of tension in particular, among others. There have been quite a few changes along the way, but I've managed to find my tennis string sweet spot, in a sense.