Personally when i was using Dual-SIM setup on my old QMobile phones, i used to use my primary Zong SIM along with a Telenor SIM. Perhaps you can do the same.
BTW, when you use Dual-SIMs, the SIMS are working individually, they are not interfering or complimenting one another. You can use any SIM with any other SIM without any worries about compatibility issues or whatever. The Secondary SIM you choose should give you some benefit of it's own. For example currently you're using Telenor, if you pair it with a ZONG or Warid SIM, you'll gain the advantage of LTE support.
Hope i helped.