If you have a suds saver function, you are well on your way but you don't have to have that feature in order to save a lot of water. The most important thing is a large tub, larger than a single laundry tub. With the suds saver feature, you don't have to tend to things as much. The main thing is to direct the water coming out of the washing machine into the tubs. I use a walk-in bathtub with a second large plastic tub on the seat area. The back of the tub is next to the washing machine so it is easy to divert the drain hoses to the tubs. I use a gentle detergent that won't cause problems for plants. Meyers, Seventh Generation, there are several to choose from. I don't use more detergent than I need to get some suds. Most instructions are written for the hardest water in the country. This sells lots more detergent. Besides wasting detergent, you may find that your skin is usually a little dry or irritated because rinsing always leaves a little behind.
I wash the light colored, lightly soiled items first and save the wash water in the smaller tub. Then I return this water to the machine for a second and sometimes third load. I catch the wash water and the rinse water in the tubs and use it for flushing toilets. Buckets, kitty litter containers, 5 gallon pails, many things work. The point in flushing with an outside source is to get a high enough flow rate into the toilet to cause the flushing mechanism to trip. I also use the wash water for watering plants or washing floors.
During the week, when I take a shower, while I am waiting for hot water to come, I catch the clean water (as clean as it gets in DC) and put it in the washing machine. After about a week of showers, I have almost enough water for my first load.
I also catch my water from rinsing dishes in a small tub and then put it into a larger bucket and use it for watering plants. Again, I use a mild detergent.
My water usage is so low that some months, I don't even have a water bill to pay.
Water is plentiful in DC, but water processing and pumping consumes a lot of energy.