The primary issue you will face with practically any vector application is the variance of colors within any given area.
The orb is easy, it's primarily white/light yellow. The difficulty is the background with all its color diffusion and variance. It works because no one area is a solid color, there are tonal changes within the "glow" that lend to the notion of dispersion of the aura.
Using gradients and gradient meshes you can get somewhat of a base.
But after that, it will require detailed manual work to create more objects in order to achieve the same overall visual effect.
There is no easy or fast method to create a similar piece of artwork in a vector application. This is why, at times, pixel-based art is actually better for some uses.