The Victoria 6 HD promo image was probably rendered in DAZ Studio.  The difference between the professional promo image and your render is posing and lighting.

This is also true of photograph. When you hire a professional photographer, yeah he has a better camera and lenses than your phone or pocket camera, but the big difference is he understands posing and how to use or create lighting. If you had his camera and lenes, you would still take boring pictures.

It is the same thing with 3D rendering. You need to learn how to do posing and lighting. There are various tutorials out there on lighting in DAZ Studio, but the technology has changed a lot in the last few years.

DAZ Studio comes with the uberenviroment light for global illumination, the standard distant, point, linear point and spot lights. Also the UberArea lights come with DAZ.

Recently a lot of people are using the Advanced lights from Age of Armour. The Advanced Ambient light can provide global illumination or can simulate indirect lighting and it usually renders faster than UberEnviroment ligts. The main advantage of the advanced distant and spot lights are faster render times, but you have to know a lot about lighting to understand how to use them and get that benefit.

I also use the InaneGlory Photo Studio - Point and Shoot 2 a lot. It gives you lights that are similar to those used by proffessional photographers in a photo studio.

The thing to keep in mind is buying all those light sets is NOT going to magically improve you renders. You need to learn how to do lighting.  Learn the basics 3 point lighting. Learn how to create dramatic lighting. You can do all that with the lights that come free with DAZ Studio.

Notice the promo image lighting. The far side of the body and face is brightly lite up while the near side had normal lighting levels with very soft shadows. This kind of rim lighting makes for dramatic images. Your image has much flatter, more uniform, lighting which makes it less interesting.

It takes practice and study to learn to do renders approaching the quality of the proffessional promo renders DAZ does.