In any kind of music the percussive element that drives music forward is something that's really important, for example, the drums in a piece, or the bass line, or a rhythm guitar. Whatever can push the momentum forward in a song is great. As far as the accordion is concerned, and the left hand, playing a really powerful bass can be great. It can be really simple and really awesome at the same time.
I'm going to start on the C, which on this instrument has a little divot. It may be hard to see, but I'm tapping it with my finger right there. Some instruments have a gem which makes it much easier to find. This one does not. Playing a really solid bass can totally make a difference in a song.
So, if I were going to do a standard 1-4-5 chord series, 1, 4, 5, 1. That's something that works in a lot of music. In jazz, or whatever, a 1-4-5-1 chord series really works and can be a strong bass line. Let's just go with that for a second and riff on it a little bit. A 1, to the 4, to the 5, to the 1, 4, 5, 1.
Of course, having a comprehension of scales for your left hand is going to help you too if you want to mess around with that a little bit. Again, starting on the C, I'll play a C scale for you. That's something to go over all the time that will really help in your playing, because the left hand is a super important part of accordion playing.