Character layout in calligraphy e.g. with respect to a quotation from Confucius
It looks there are quite a bit of concepts in your question.


Tang poetry. Typical Tang poetry style is 5x4 or 7x4, with a bit more variations.
Layout of Chinese calligraphy. It's not necessarily 5x5. Don't be limited to that. Any size is okay. The typical layout is top to down, and right to left. For the layout of your mentioned Confucius, just write it as this layout with same characters in each column, without punctuations.
Best script for starter. The "calm" effect comes mostly from "Regular scripts", which is recommended for beginner, even for experienced ones.
Recommended process. I suggest you to copy 颜体（颜真卿）from the beginning, instead of writing your own. This is the most famous and respected Regular scripts. But I'm not a calligrapher. The teacher may has better and more specific recommendations.