While you can make more doing a simple two way run of bulk commodities in a T7 than a long distance rares run, I find it really boring. When I had my Asp, I did a circular rares run using around twenty six stations and frequently had a full cargo bay of 112T. It didn't take long to be able to afford a T7 so I upgraded. At first I tried a two way route carrying 208T each time. If I pushed it, I could make a return trip in around fifteen minutes for a 500,000 cr profit, so making a couple of million an hour but I just can't stomach doing more than four two way runs at a time.
So, I decided to go back to my rares run but modified it by integrating one way loads of ordinary goods into the route. Basically the first time I ran my usual route, I checked Thrupps and Slopey's trade helper apps to see if there was anything I could carry at a decent profit to the next rares station. There were only a few that worked that way as most of the stations on my route were agricultural ones. So, I then looked to see if there were any systems en route where I could pick up something from an industrial or high tech system that the agricultural system would want to buy. In most cases Thrupps or Slopey's could find somewhere within 20ly of my destination that could supply me with a commodity that would make over 1000 cr per T. I'd stop by and top up my 208T hold to capacity then continue my journey. My twenty six station rares run became a forty station run instead but added a couple of million profit to each circuit.
Although it's probably less profitable than doing a simple two way repetitive run I found it lot more interesting. Anyway, it only took me a little over a week to accumulate enough credits for the Python, which I have now. Unfortunately that has a much shorter jump range so I've been forced to go back to two way, short distance trading on the whole.