Because this is for your own wardrobe, only you can decide what is best for your needs. The best that anyone else can do is just to give out different ideas to choose from that you may not have already considered.
In most cases, people are looking for more efficient use of their closet space. The simplest part of this is to double the number of hanger rods for hanging clothes. Use 1 rod high and 1 rod low. Putting a shelf directly above these rods won't help with storage space, but it will reduce the amount of airborne dust from falling on those clothes from above. However, don't forget to leave enough areas with just a single rod for longer clothes, such as dresses.
Instead of having a rod span a really wide area, split it up into smaller sections for better organization. That way you can have one area for one type of clothing (such as dress clothes) and another area for another type of clothes (such as work clothes). For better aesthetics, separate these areas with another feature, such as a stack of drawers or shelves.
For seasonal clothes that may not be used for long times, you might even consider adding doors in front of those areas to reduce the amount of airborne dust falling on them when they are stored for longer periods.
Consider what types of things you would want on shelves versus in drawers. Some people prefer more shelves, others prefer more drawers. An interesting idea that one client came up with, was that they wanted more drawers, but also wanted to see what was in them (like an open shelf). So I made frame and panel drawer fronts but with plexiglass panels so they could see inside. The height of a drawer depends on what it needs to hold. For example, a sock drawer can be very tall, but a drawer for sweaters may be very shallow so you don't have to dig through as many layers to find what you need.
If the closet contains a narrow nook that otherwise wouldn't be as useful for other articles, it would be a great opportunity for a rotating shoe tree or lazy-susan (as they are called here). It makes good use of an otherwise less useful area.
The primary material is best to be melamine, but that can get a little boring too. A real nice look is to have some wood contrast to go with the melamine. So even if you have white melamine shelves, it looks nice to have a contrasting wood front edge.
Oh, here is another interesting idea if you have a lot of high storage space. I had a customer that wasn't very tall, but had a lot of high storage in her cherry kitchen that I built. So she asked me to make her a decorative 3-foot tall folding cherry ladder that would stay in the kitchen. Instead of finding a source for the ladder hardware, I went to the hardware store and bought an ugly wooden ladder, and then rebuilt it with cherry to match her kitchen. I painted the plain metal, and replaced all of the rivets and screws with brass nuts and bolts.