'll say it depends how you play... if you're a frequent string breaker try the hybrid string like : prince problend, or wilson nxt duo. if you want touch try Gamma TNT Fusion2 19G... even though it's 19 Gauge it won't break easily... other good ones are the Luxilon Big Banger s string those string will last you a long time... but if you really want a good string and you have the money for it try some of the natural gut, but don't put them all for the cross and main... try to put natural gut for the cross then put a regular synthetic gut for the main(vice-versa) for durability and playability. I myself have been using the Prince Tour Blend, and it's very good
I hope this will help you