I'm pretty consistent with the types of brushes I use. When I first started painting, the teacher gave us one large flat brush (1") and one smallish flat brush (1/2"). We didn't get any round brushes, we didn't have any fancy fan brushes, nothing was particularly high quality or special.
There were a few reasons for this. One is that students have a tendency to get buried in tiny details. The composition shrinks to the size of a golf ball, even if the support is 2' x 2'. This is something I have found true for most young students... they want to make convincing details while ignoring the "big picture" so to speak.
By not giving them the tools to get buried in the details (ie a 30/0 liner brush) they are forced to deal with making the larger elements of a painting work.
Also, like having a hobby or a sport, tools have a tendency to make people reliant on what that tool does, rather than learning how to nail down the basics without the tool and picking up a tool here and there for ease of execution or enhancement.
Take something like golf for example - a great golfer can use a set of average clubs with excellence, they can take their sport to a whole new level with really high tech clubs. You rarely see someone achieve excellence in golf having started out with all the bells and whistles and needing a specific tool for every specific shot... there is too much reliance, not enough base skill. Take away the fancy clubs and what is left?
This background has stayed with me. For years and years I painted with the same two brush sizes (actually literally the same two brushes.... one of them I almost wore down to the ferrule!) I didn't worry about having the right brush for the job, I just worried about learning how to paint. Once I got those basics down, then I wanted to explore a little more in my techniques and that is when I started out trying an angle brush here or a filbert there.
One thing I never understood is the traditional artist brush depiction of the fat round brush dripping with paint. (You know, you look at cartoons and there is a man with a curled mustache and a beret with a palette slung over his thumb, holding this big brush drooling paint.) This is pretty far from reality for me as a painter - those big round brushes are the WORST thing for me to use. I never ever got the hang of them and gave up experimenting with them long ago.
I still mainly use flats (same sizes), I throw in the occasional filbert and most of my lines are done with tiny rounds or spotter brushes (ACEOs need eensy teensy brushwork).