My plants are all inventoried here on garden.org plant list. I'm slowly filling in the comment section for each one - I'll keep track of things like
Whom bought from and date purchased I used to maintain Excel spreadsheet, but there's so much more info / links here at garden.org that can be accessed via plant list function.
As for labeling, hubby recently bought me a Brother P-Touch
https://www.amazon.com/dp/B00OCEKCDA/
In the past, I've used old vinyl blinds - marked with pencil. I found pencil lasts longer than a sharpie. Works pretty well.
I'm going to order stainless steel stakes from:
https://www.amazon.com/dp/B00OCEKCDA/
Lynn and Richard of Wisconsin Garden Video Blog did a great video on Kincaid labels:
https://www.amazon.com/dp/B00OCEKCDA/