Any advice on how I can make this render better?
Exposure seems a bit high in general, and I'd put a key light or rim light into the scene to balance things out. If you're using HDRI lighting, you'll need to balance the environment light with the scene lights, or get some new HDRIs that mimic extra lights. (like Click N Render IBL) If you're fond of your backdrop you can always render without the dome and put it back in post. If you're not sure about exposure at all, there is a little tool to calculate and set it for you when iray is the active viewport display mode. It's right next to the button to switch, and just drag a box over the brightest part of your model to have it calculate exposure for you. If you ever really mess it up, Exposure Value of 13 is default in Render Settings.
m4dsk1llz is right about editing things in post, and you can also do vignetting right in DAZ if you want.
Eyes are the other thing that sticks out as something that can be improved. Her lower eyelids seem too open to me. She's not quite looking into the camera in a studio style photo. If you are using Genesis 8.1, there are some fairly competent automatic eyelid controls, but you can never go wrong by manually tweaking until they look right. For the eyeballs themselves, select each eye, and set Point At to your camera for easy alignment. This will slow down your scene a bit if you need to adjust the camera and your PC isn't strong, and you'll need a camera set instead of just perspective view.
Do you have a bend morph package? Depending on if you like neck tendons and knee details to be visible, there are a number of solutions that will add in those details that DAZ doesn't. They also correct a lot of weird leg and arm bend behavior. U.N.B.M, Auto Shape Enhancer, and Chameleon Rose for G8 (all can be found on this site) all will help there, and each work similar but look a fair amount different. Mix and match or find your favorite.
If you are quite new to DAZ, or haven't gone into a lot of guides, you may be rendering on CPU instead of GPU. If you have an NVIDIA graphics card, the Iray renderer is a lot faster on it compared to CPU. It's easily 30x faster, even comparing a $500 CPU to a $250 GPU. Go to Render Settings, click on the Advanced tab, and ensure you have only your GPU selected to force it to render on the appropriate hardware. If your GPU is part of the 10 series (like 1060), you likely will need to update your GPU drivers to ensure that Iray is compatible. There's a lot to say here about optimizing for less powerful hardware, so if you think this is applicable feel free to PM me.
Edit: and if you're using a not so great PC, set your model's subdivision level low enough that you can pose and morph without waiting too long for it to appear in the viewport.
