This type of clothes rack can be as simple or as difficult to make as you want it to be. I added a level of difficulty because we need them to be portable and take up as little space as possible when in transport.
This is what we're going for:

Tools that will make your life simpler:
- Skill saw or some sort of electric saw
- Electric Drill
- Drill bits (size dependent upon your bolt size)
- Phillips head drill bit
- Spade drill bit (size dependent upon your rod size)
- Bolts, washers, nuts (I used wing nuts for assembly without tools)
- Four 3" angle connector hardware (should look something like this.
- Twelze 1.5" angle hardware connector. Same as this, but smaller. (HINT: the back of these packages will tell you what size of bolts to get. Make sure that they are longer than 2.5", as the bolts will be going through the 2"x2"...)
- Two 2" x 2" boards. I cut mine to 5 feet tall. This will determine height of your rack
- One 2" x 6" x 8' piece of lumber
- wood screws that fit those 1.5" angle connectors
(I try to obtain all my lumber by dumpster diving at construction sites. Be sure to ask permission first...)
Instructions:
Start by cutting your 2"x6". This will be your base. Cut two pieces 22" long and four pieces that are 8" long.

You're going to connect these pieces using your wood screws and 1.5" angle connectors. To do this, I lined them up first on a flat surface and marked the eyes of the connectors with a sharpie. It's not an exact science, but you will want everything to be as square and level as possible.

You then attach the hardware to the top of the base. I used my vertical poles as a pattern to make sure everything was snug. I also used a
triangle thingy to make sure I was in the center of the base.

Next, you place your vertical pole in between the brackets you just attached and mark your holes for drilling.

Then you drill your hole(s) for your cross bars. (We used cheap-ish curtain rods found at IKEA for our croass bars. The curtain rods, being explandable, are what makes this rack expandable...)

Finally, attached the vertical pole to the base. I did this using bolts and wing nuts so that power tools would not required to assemble/disassemble.

Repeat all of the above for your second stand.

Here is in action: