Genesis is UV Mapped for V4, M4 and K4, so any V4 skin maps that you have can be used on Genesis. Most V4 clothing will fit to Genesis using the Autofit plugin (M4 and K4 as well), and several others if you buy the ‘iconic shapes’ packages which supply a clone for Autofit. In other words, if you buy the Gen3 Iconic Shapes bundle, Gen3 clothing can be made to fit Genesis as well.
There are no Morphs++ packages for Genesis, but there is the Evolution Head and Body Morphs which do much the same thing, and I would say these are essential if you want to create your own characters. There are loads of free items for both V4 and Genesis at ShareCG, and many other places too.
There is no need to buy anything immediately, you have DS4.5 Pro, and Genesis is free with that, along with some clothing. You could try Autofitting some V4 clothes to Genesis and see how you get on.