From what I've heard from people who have reached Elite trading rank, there is no secret to it (after finding a decent route) - just focus on being as efficient as you can and do the grind.
Two people I've read about of that have reached Elite in trading are:
Changtau2005 on the official forums:
https://forums.frontier.co.uk/showthread.php?t=100464Two other people in that thread mentioned reaching Eilte (one who had the money for it but wasn't awarded the rank at the time, possibly due to a bug), but I haven't tracked down their posts.
Here's a video of him doing a luxuries run at Tenche:
https://www.youtube.com/watch?v=VyOSIPpVUTMKornelius Briedis:
https://www.youtube.com/watch?v=jzjvTJSnIe8I don't know if a T9 is more effective for luxuries run due to its higher cargo capacity or an Anaconda due to its ability to get in and out of the station faster.