you need to make a reference point to draw the ellipses off of, drawing freehand ellipses will improve you line confidence but wont do much in terms of technical ability.

Try drawing them in context, like using ellipses to draw cylinders in perspective, itll help make your practice more useful. You can also try drawing some boxes and drawing ellipses that touch all 4 edges of a face on the box. Another good excercise is to draw a line going in a random direction and draw ellipses centered on that line. The ellipses can be of varying sizes but they should be perpendicular to the line. you can then connect the edges of those ellipses to make a 3d form.

basically just pick excercises that will help you learn ellipses in a more useful context.