MySQL optimization

I have a Linode SSD VPS (4GB RAM and 2 Cores) running latest Debian 9 with Apache Virtualmin. Into this webserver I have some virtualhosts with some Wordpress and Mautic installs. I would like to optimize MariaDB to run those applications very very very very fast. Using as much RAM memory is possible to cache almost everything. Please I am looking for someone with deeply knowledge of MariaDB. The person must create a simple step by step "how to guide" explaining what and why should be done to optimize MariaDB in my application cass. Because I would like to be able to apply the changes by myself and understand why they changes must be done.