heyRavenna; Since nobody else has attempted to provide any advice I will offer the following:
a) Remove the moss completely from the soil and tree trunk to get a better look at the nebari and to allow the soil/roots to breathe better.
b) Remove the berries/seeds to direct more energy to the foliage (unless you plan on exhibiting the tree in the near future and want to feature the berries).
c) Find out if the whitish growth on the foliage is natural or some sort of fungus/mold/whatever. This is hard to determine from photos so take it to an experienced nurseryman or horticultural expert.
d) Next you need to decide what size and form you are looking for in the future. If you envision a larger profile you need to place it in a larger pot or growbox. As far as suggested forms or styles it is not very easy (or wise) to suggest something unless one can see the overall structure and branching and this is hard to do with pictures because of the foliage density.
e) Since you are participating in the Crespi bonsai school I would presume that they would be an extremely valuable resource in answering all your questions. Remember, if you do not seek and take advice from a professional instructor (which you are paying to teach you bonsai techniques) you will not get the benefits you signed up for.
I have not worked specifically with needle juniper as they are not very prevalent in the US. My advice is based on generally accepted bonsai and horticultural pricipals. Regards, heyMikey!!