There's a free 30 trial download available. That's your least expensive option for getting your feet wet.
Will the skills learned with the client version directly transfer to the server version?
Compared to scaling up an Access database to something like SQL server, scaling up a basic install of filemaker for use on a server version is a piece of cake. For the most part, you simply upload your files to the server and start using them. No file conversions or data migration needed.