Let me see if I got this right. So you are already scheduled to take a Bonsai class, and you are looking for Yamadori. First of all, collecting from the wild is not a task for beginners, secondly, I think it is not the right time of the year to collect a pine, and thirdly, if you collect a specimen you have to let it be for at least 1 year, so it recovers from being collected. A pine, I would guess it needs a lot more than a year. And yes, these trees are way too young to do anything on them other than letting them grow.
You should just get a nursery plant, get a boxwood with a decent trunk. Or a Juniper. I personally recommend Juniper. You can also get a nursery grown tree such as maple or oak and chop the trunk.