What costs do I need to consider?

I'm a newbie starting to plan a Dolpin project. Other that the cost of the Dolphin licence and the monthly hosting fee, what other costs might I need to cover if I was to go with hosting on a dedicated server? (For example I just found out I might want / need a cPanel licence, but there's probably more things I haven't thought of).

For a dedicated server you can use Webmin to do everything you might need and it is free.  I recommend vsftpd as your ftp server, I had issues with some other ones and vsftpd installed without any issues.  phpMyAdmin can manage any database changes you may need to do.  Other than what you have outlined, you might want to budget for third party modules.

 A lot of it is going to depend on how much experience you have in running a server and your level or programming knowledge. I know if I had started out with a dedicated server I would have been in way over my head.

If you have no experience with either you're going to have to budge a pretty hefty amount for someone to run the server and fix anything that goes haywire.

My first use of a dedicated server was when I started the Dolphin project last year; around July perhaps.  I first started with the VPS but dumped that soon after I started the project.  It depends on how good you are at following tutorials I suppose.  However, it is possible that if you can not get the dedicated server up and running that you will need to hire someone to help manage it.