I've been using a Bullet Journal-inspired method for years. I've been keeping a Moleskine notebook with me on my desk and in my bag since I first heard about the method 4+ years ago . I quickly found out that sticking to the method exactly was madness. It takes too much time. If I spent that much time just organizing my notebook, I wouldn't end up using it at all.
My system involves 1 moleskine notebook (Large, Graph Ruled, soft or hard cover) for the year as well as a Lamy Safari. I could certainly use cheaper materials, but I like the feel of using these tools. I keep my pen with my notebook with a Quiver.
At the beginning of each year, I first review the tasks and events that I entered in the past year's notebook. I then leave a couple pages for an index and add the yearly calendar, yearly tasks, and yearly goals. While the tasks are very specific, the goals are more general and mostly serve as a grounding for the start of the year. At the beginning of each month, I create a monthly calendar and a monthly task list. The calendar is mostly just copied down from my Google calendar. I don't really refer to it, but it serves as a review of the upcoming month.
At the beginning of each day (or sometimes at the end of the previous one), I enter the task list for the day using boxes. I enter events for the day with circles (and include the people at the event, if I can). I enter information (things like "Biked to Work") with a dash. I typically have 3 sections separated by a blank line-- personal before work, work, personal after work. I like keeping track of my tasks at work so that I can refer back to what I did each week and keep my supervisor up-to-date on what's going on. I sometimes put other lists in the journal, but mostly I do that in OneNote. I rarely put meeting notes or anything like that in it. I would just end up running out of notebook quickly. Also, I prefer being able to rearrange meeting notes into more logical groupings. Projects are not inherently chronological like daily task lists are.
I don't worry about skipping days. If I miss a day, I leave a small blank spot and move on. I typically backfill weekends on the following Monday. Some months, I don't remember to fill out the calendar or task list until I go to do it for the next month. I typically fill out the index only two or three times a year. I don't really use it much, so there isn't a reason to obsess about keeping it updated.
If I were worried about filling in missing information or how I'm not following the system exactly, I would end up putting off entering anything at all until I wouldn't think about it at all. In the end, the best system is the one that you use.