I want to make these 6 dots http://prntscr.com/e29gxm move alongside a mask path so I wouldn't need to animate the whole thing since I would need quite some calculation how to do it in a same speed across all lines.
Since I would do more motion graphics I guess this method could be applied to more projects.
All help or other methods of achieving this are very appreciated.
i'm not sure if you tried this, but you can copy/paste a mask path as a motion path.
twirl the mask properties down, select the 'mask path' property and copy that.
select the position property of the layer (dot) that you want to follow that mask path, and then paste the mask path (which will then become a motion path). you'll see the mask vertices as keyframes, and can adjust those keyframes as needed.
to create the repeating dots, you could try adding the echo effect to the dot layer, adjust the number of 'echoes' and then adjust the echo time to see if get offset that you need to have them follow around the mask path.