I will be downloading Moodle and installing for the first time. I do not have previous experience and need help with the amount of databases I may need. If there will be different clients using the site and they want their own customisation, will I need a separate database for each client?
This is called multi-tenancy. It depends on what you want. Do you need each client to have a completely separate experience? At the simplest level you can just have one site and look at Course_categories (to represent a client) and category themes.
You can have completely separate Moodle sites per client.
Or.... have a look at www.iomad.org (which is Moodle extended with multi-tenancy functions)
You can have completely separate Moodle sites per client.
Or.... have a look at www.iomad.org (which is Moodle extended with multi-tenancy functions)
Just in case, the "low tech" is to run independent Moodle instances on the same server - either as http(s)://example.com/client1, .. or as http(s)://client1.example.com, .. or even http(s)://example1.com, .. For each there will be a code tree and a database. More flexible when it comes to customisations, but also more work in maintaining a Moodle site for each customer.