But what do i do after those few weeks? what do i feed them then? Also can i put my seeds directly in the 12-15 gallon hole or do i absolutely need to do it in a smaller pot then transplant because i really dont see the need in doing so
You do not need to transplant. You can just do it like you are talking about. I would keep feeding them after those first few weeks. Personally, I use the Fox Farm lineup: Big Bloom, Grow Big, and Tiger Bloom. I do not have much experience growing outdoors so hopefully someone else will chime in on any specifics. Using the Ocean Forest will make a huge difference instead of just planting them in the ground, though.
Your best bet is to plant them and while they are working through the nutes that come with the soil, do all the research you can on how to diagnose different problems and how to fix them. Depending on the strain and how much direct sunlight they get, they might get huge. You should start a grow journal on here. Lots of RIUers follow those and are more than happy to give advice on anything you wish.
I would like to help you more but I am an indoor guy until I can grow legally, then I will migrate outdoors. I would hate to give you bad advice.