Some tools I would recommend.
A lightweight tripod. You also can buy a monopod. There are monopods with a "small tripod" on the base.
A luminous lens. On Canon you have the 50mm 1.8 lens very cheap, excellent optics... but it is slow as hell on focusing. That is why some people use continuous light to aid focusing, because you have a very narrow DOF. But to be honest, you probably need a wider lens on a wedding for the group shoots. And probably you won't shoot in f/1.8 on a group photo because someone is going to be out of focus. Another feature to look here is a lens with optical stabilization.
Here comes the tricky part
The annoyance of a built in flash is the flat light it provides. That will happen to you with a ring flash too. That gives you an urban paparazzi look. But probably you don't need that.
- Go for a speed light with radio receptor and a remote trigger.
There you can go with 2 options: Manual or TTL. A very nice option for manual are the Yongnuo YN560 III and Yongnuo RF-603 trigger. (In some cameras you also can fire it remotely using 2 of these.) There is a new model IV. I'm not sure about the differences.
For TTL there are several models from the same brand like Yongnuo YN568EX, and you have some options for TTL trigger. The details on the different options on TTL triggers are a little out of the scope of the answer. But take a look.
One useful feature on a TTL flash on the camera is that some models can send a light to aid focusing.
- If you are going for a speedlight and a wireless remote trigger, your next asset, besides a light diffuser for the flash, is... an assistant.
He can provide you directional light, he can light a wedding couple from 3 meters and you can take a photo from across the room 15 meters away to have a panoramic view.
Look for some tutorials on how to combine ambient light with a speed light... You will love the results.
- The most expensive option is buy a new camera body with a really high ISO setting.