As an independant learner, I doubt anyone will ever need to read what I write in ancient greek except myself. I just aim for making it easy to write and making it similar enough to what is printed in books/websites that I can identify it easily. And when I write Greek on the computer I just use transliteration, since I do not want to go to the effort of getting a Greek font on one of my word processors.
An interesting phenomenon is how my long term usage of the Roman alphabet (since I was 4 years old or so) influences my writing of Greek, and lately my Greek writing is affecting my Roman alphabet (English) handwriting. I have always had a very distinctive way of writing the letter 'a' (probably the easiest way for someone to identify my handwriting), which is different from the alpha. Sometimes, when I write alpha, I accidently put an 'a' instead, in which case I flip the pencil and get the eraser to work. And recently, instead of writing my distinct 'a' in English, I put in an alpha. There are other examples, but this is the clearest.