anyway, RO/DI is not just to remove chlorine that simple. It involves many water purification stages to create pure H2O aka water. The benefits of using RO/DI water is zero introduction of NO3/PO4 and other harmful substances into your tank.
Having said so, i'd suggest you can temporarily forget about RO/DI water. Get the fundamental stuff in place first. For instance, skimmer, lightings, husbandry skills etc.