When creating objects with volume and shading like a balloon keep the shape of the object in mind. A linear gradient on a round object will look odd, a radial gradient might work better, or a duplicate of the base shape in a lighter colour with a Gaussian blur placed inside.
You can make one balloon e.g. a bright red and then use HSL adjustment layers to change the colours - or go in and colour the base shape [and the lighter shape inside the clip and the knot shapes] individually.
As always, it's about variations. You can play with gradients, shapes, and effects. Just try and think about the shape and the texture [for the balloons that would be a little shiny [not full on metal reflective] and a bit transparent [not totally see through and less so at the edges]]. Enjoy!
