This is a problem that we all face. This forum has a great many tips, tricks, hints, and insights. That is the good news. The bad news is, when you are starting out, this forum may not be the best option to read quickly. I’d suggest in your case to do a search on “new to omnifocus”.
Staying on your main question, my suggestion for a layout for your case might be to set top-level folders based on SEASONS such as Spring, Summer, Fall, Winter, and Anytime. As needed, you could define this further with years, such as Spring 2017. Then, create sub-folders for each goal that has to be done in each particular season. For example, you may purchase new seedlings only in the Winter, so create a sub-folder Winter 2016 / Seed Purchases. After that, create your projects that must be meet to complete the folder. One suggestion here is to make your projects “digestible” and “timely”. The first means, make the flow concise and logical so that you appreciate it not only when you create it but also when you go to do it. The second means, make the project have an outcome in a time period that you can appreciate. Open-ended “learn the guitar” projects are bound to be a source of never-ending frustration because they can eventually go nowhere and take forever and ever to get there.
BTW, the “what is important” part should start at the TOP level and percolate down to how you set up OF. Unfortunately, when you try to go the other way, from tasks in OF working up, you will quickly get lost in the forest for the leaves (a pun you might appreciate). Imagine for example that you spend two hours meticulously hand-cleaning bud worms off one apple tree and then realize you have 100 more trees to finish, and you wanted to be done tomorrow. This was rather a bit reversed in thought process to determine what is important, don’t you think? I’d be out on a spray truck with the latest green bud-worm killer already, as an example.
My final thought is, don’t be afraid to iterate in OF on different options as long as you don’t make the iteration a private game. IOW, you won’t get it right with OF the first time, but don’t make a habit of thinking that you should change what you have just because it still seems a bit hard. Settle in to something first, try it out for a few weeks, then re-evaluate.
The forum is a good place to keep asking questions. It’s got a great group of very knowledgable and friendly folks. So, keep plugging at it here as you need.