Get a flash and experiment with it.

You don't need a 'person' to sit as a subject either, just use something appropriate.
Try direct flash, bounce flash off the wall, ceiling etc and see what the difference is. You can have a huge amount of fun with your flash on camera and your photographic needs may never take you to off camera flash, so take your time and enjoy yourself.
If you want to go off camera with your lighting then you will need to start considering just where you're going to shoot - if it is in a studio location and doesn't need to be portable you may decide that 'speedlites' are not the way to go.
Welcome to a whole new way to spend huge amounts of money!
On that note: you don't need to buy 'Canon' speedlites either. The Nissin Di622 (119 quid on amazon) and Di822 are great at half the price of Canons and come with built in diffuser, catch light card and variable power settings.