Solo project work flow

I've been working on learning software development in my free time for a while now. Have been just doing the independent learning thing and learned most of what I know going down rabbit holes attempting to build something that frankly was too much. I don't regret the time I spent on it, as it took me through just about every aspect of full stack development. I learned enough to contribute code that is in use on an open source android app, so I definitely learned something useful.

After taking a break from it I'm ready to start building some (more reasonable) projects to use for a portfolio. Although I want to not over do it like my learning project, I'm aware that to stand out as a self taught guy, quality projects are a must. I've got some ideas I want to build but before I start I'd like to focus on how I'm going to approach it in a structured way, opposed to chasing that rabbit hoping it all comes together in the end.

It seems there isn't a lot of info on work flow for independent work. I know coding on an island isn't good (figuratively; literally coding on an island sounds nice), but it seems necessary for developing a personal portfolio. Unless I'm missing something, agile seems more like a team oriented process and that's what I find the most of.

I'm just looking for some resources or guidance on how to go about starting my portfolio projects. I know it might not be easy to give advice not knowing the projects or my abilities, but maybe someone knows of a good resource or methodology for approaching software development that isn't based on managing an entire team of people.