cut away all on the left up to half way and the downward on the right and go for informal upright maybe?

It looks like IT wants to be a cascade. I'd let it be one,especially for your first Bonsai.
Is that a glass/plastic pot? Drainage holes right?
If it's been in a store gradually work it up to full sun ..Outside.(weather permitting)
When you decide to repot it I'd loose the green rocks and put it in a brown clay pot. Maybe a shorter 8sided one. Your taste are the rule here.
Read everything online/books that you can find and learn how to take care of your juniper. Get a plan in your mind of what you want the future Bonsai to look like .(reminds me of a dragon starting up and flying down the mountain)But thats just me (;
Wire,repot,trim at the proper time as it fits your overall plan for the future Bonsai.
Good Luck
R

The ancient practice of bonsai lifts pruning to an art form level. The pruning techniques for bonsai not only reduce the size of the plant but strive to mimic the natural forms of the trees that grew in the mountainous, harsh regions where bonsai originated.

One of these popular forms is the cascade bonsai. Creating a cascade bonsai is intended to reflect the shape of a tree that has had a difficult time, yet perseveres. It is best to imagine a shape that was formed due to the crushing weight of heavy winter snows, land slides or mud slides. These natural catastrophes will twist the tree downward in nature and so it is with a bonsai in the cascade form.

The main trunk of a bonsai in a cascade form will bend downward, past the lip of its container and past its root line. The branches on the main trunk will reach both out and up, as though it were striving for the sun.