The two things you should figure out first are how much padding do you require and what seat width is best for you. I suffered in my early road riding days with seat discomfort. Turns out that my bibs were the problem. By chance I caught a deal on some triathlon shorts and even though I prefer bibs, thought I would try them. BAM! It was perfect, the much thinner pad was better for me. Some bibs have excess padding for me and bunch up. I can ride centries in thin tri chamois clothing. Prefering the benefits of bibs, I now buy tri suits and wear them by themselves or with a jersey over them. LBS told me about some bibs they sell that have thinner chamois in them, so there are options out there. My saddle has very little padding and I feel that I could almost go with no padding. I am short of stature and light weight (get down to 129lbs in summer) and too much padding blocked blood flow and took up too much room down there.
Figure out your optimal seat width too. LBS let me try a Selle SMP saddle, it has a very wide open channel running down the center of it. Did a thirty, a forty five and then a fifty mile ride with it and had soreness in my hips. Made me walk funny for two days and felt like I was doing damage to my hips. It was simply too wide for me.
I have a cheap saddle now and sometimes want to change it for a nicer saddle, but I follow rule number one. If it's working and not hurting, don't change it.
When I get a custom bike built my saddle choice will be something with very thin or no padding and something narrow (I will measure what I have now). After that I will look at gram numbers.