What are you trying to learn? Did you learn it?
Before you dive in (with any tree) make sure you ask yourself - what exactly am I doing?
I am going to give you some constructive feedback on your tree. It doesn't look to me like you had a design in mind when you started pruning. You just stripped branches from the bottom 1/2 of the two trunks and then called it a day. There was no wiring, no further development of the upper foliage mass. The tree doesn't look like anything right now other than a nursery plant that had some branches removed.
This is all fine - you are a beginner - and we are all beginners at some point. But you can continue to do what you just did (in terms of trimming trees randomly) and ten years from now be no further along in terms of developing skills to make good bonsai. The fastest way to develop skill is to follow someone who already has skill. I always recommend joining a club and going to convention workshops, but if that is not practical, there are some great streaming video resources available (make sure they are from reputable sources that know what they're doing).
But another good way to learn is to see a nice bonsai... and try to make the exact same thing. Try to copy it EXACTLY. That way even if you don't totally know "why" you are only removing some branches and leaving others, you are working off a blueprint. Then even if your tree isn't perfect, it might be 50% perfect, which is a lot better than 0% perfect
I shared this video in another thread and I really like it because of the way the artist rotates the tree so you get to see it from all angles. This is a procumbens juniper - the same type of tree that you just pruned. It looks very different. What you are seeing is not different material - it is the experience of the artist.
Some of the things you can certainly learn from your tree is how junipers respond to being transplanted, how much they like your soil mix, and how a juniper responds when it has half of its foliage removed. These are all really good things to learn.
I don't want to sound like a crabby old man in this thread - I am trying to save you from making all the mistakes I made
I already have a green house in the back, a table top, 6 permanent trees, 3 dozen "project trees"...not to mention the cost of pots and soil...blah blah blah...It's an expensive hobby, and nothing kills those like an unhappy wife, so if she wants me to plant some of them in pots other then the drilled together trainers...gonna say yes.
The extra 15 minutes of price comparing normally results in very good savings.
