I will try to answer as much as I can. But please know that what you are asking is a huge subject in itself and needs months to study, practice and master. You may want to start by just doing a google and learn about how to design tables, databases and entity relationships. There are plenty of tutorials online for free as well as videos on youtube.
The table schema that you have outlined seem to be normalized enough. You can read about normalization and its advantages
online[
^]. Again there are plenty of tutorials for free. Please try not to understand every Normal Form straightaway, as they take a bit of time and experience to really make sense. It is okay to learn slowly.
Regarding diagrams: Do not confuse between a
Table schema diagram[
^] with an
ER diagram[
^]. They are totally different things and sometimes used synonymously by people who don't understand them. For your purpose a Table Schema diagram is what you are looking for.
Free tools such as
Goodle Draw[
^],
Gliffy[
^] and
Lucid Chart/[
^] can come really handy if you don't have MS Visio.
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