The imperial primer, as you can guess primes the model before painting and may help paint stick to the model, especially for finecast or metal. You have a lot of foundations but not a hell lot of layer paints but I would begin painting the majority of the model such as chest, face helm, legs etc. a foundation colour of your choice depending on the chosen craftworld the pics could also be a handy tip for what should be what colour etc. usually after painting the foundation put a wash over it either the colour of the model or nuln oil. Then begin adding the layer colour of your choice on higher parts where the light would touch on the model or in a particular design of a specific craftworld. The start painting gem stones you will need the technical called "ard coat". Paint the gemstone using a technique similar to the chosen colour here.
good luck
thanks for the help, couple of quick questions.
1. when you say wash over it, do you mean with the foundation colour or a colour in the 'colour' range, or a colour in the 'wash' range?
2. the layer part, is that like a second coat or highlighting with a brighter colour than the foundation/wash combo? for eg. edging
will definetly get ard coat this week!