Sounds like you have had a very similar progression to myself. I got the game last Christmas and played it without doing any gold rush type cash runs, just the odd RtR session until I got an Asp. At that point I only had maybe 150M. Then about 2 months ago I finally decided to hop on the passenger run train and saved up enough for a Python and did the Parutis-Medb passenger run for about a fortnight, and went to over 1B credits in that time. Up until that point I was ok with just playing the game normally, doing missions, not even stacking them, and pottering about, making cash "realistically", no board flipping etc. For a considerable time I thought that's how I would always play the game, and there are people who do do that still.
But then comes the point you realise just how much cash you do actually need to do anything beyond this type of progression, and you realise playing "normally" it will be actual YEARS before you can afford any of the high end ships and A rate them etc. Once you give in to the easy money way of life after you've worked up normally to an Asp at the most, then it starts a next phase type of enjoyment of the game. Anyone new to Elite reading this, this is how I would always recommend anyone starts the game, don't make a beeline for an Anaconda straight away, don't do gold rush exploits immediately, play it normally with occasional RtR until you get to an Asp, and then a Python. Then, if you ask me, you've earned the right to really enjoy the game without having to worry about money, by using the most efficient serious money making methods.