In what ways can I personalize a journal?

Are you talking about decorating a physical object, like by making a cover for it? If so, are you speaking of a paper-covered spiral notebook, a hardcover book with bound pages, a looseleaf binder, or what?

Does “invest” mean time, money, or something else?

Are you asking about what to put in it—i.e., how to personalize the words of your journal entries?

Sign it

I’m not sure what you are asking but a leather bound journal would be better for the page falling out syndrom. The cost is the only con I imagine. You could order one with your name on it embossed.

If you are thinking of adding objects and photo’s maybe a flip file is better with plastic pages or sheets. You can also have an online journal and decorate with graphics.

By investing I mean time, money, and thought.
Also I’m trying to decide on what type of leather, how the pages will be bound, the type of sheets used, etc. Sorry for the vagueness.