I do not want to buy a dedicated rice cooker and I have been told by some people that a rounded bottom thick Dutch pot is best for rice cooking on a gas stove I have also heard that a tall aluminium pot is best, what do you think?
It depends on how much rice you're trying to cook. I rarely cook more than a few cups at a time, and I don't use a special pot for it (clad steel, though). Once the water comes to a boil, turn down to low, leave it for about 15 minutes (covered!), turn it off, wait another 15 minutes or so (still covered), and you're done.
If you're cooking a lot of rice at a time, a thick/heavy pot (enameled cast iron, or just a heavy clad steel pot) will help hold a low temperature without scorching the bottom of the rice.
I cook my rice on a Aluminium (mostly flat) pot on a gas stove on low heat. The only trick I use is to barely cover it with water and add boiling water as it absorbs or evaporates.
I dont't cover the pot, but I usually don't cook more than 1.5 lbs at once.
I keep adding water "until done" in SMALL batches.
PS:This (I don't know why) doesn't work well for short-grained rice.
The heat from a gas stove is not evenly distributed throughout a pot or pan. Gas flames spurt upward in a ring of flames. Because the flames are beneath the pot or pan, the cookware must redistribute the heat throughout the pan so the food contained inside is sufficiently cooked.