Some tools I would recomend.
1) A lightweight tripod. You also can buy a monopod. There are monopods with a "small tripod" on the base.
2) A luminus lens. On Canon you have the 50mm 1.8 lens verey cheap, excelent optics... but it is slow as hell on focusing. That is why some people use continus light to aid focusing, becouse you have a verey narrow DOF. But to be honest, you probably need a wider lens on a weding becouse the group shoots. And probably you wont shoot in f1.8 on a group photo becouse 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 anoying of a built in flash is becouse the flat light it provides. That will happen to you with a ring flash too. That gives you an urban paparatzi look. But probably you don't need that.
3) Go for a speed light with radio receptor and a remote trigger.
There you can go with 2 options Manual or TTL. A verey nice option for manual are the Yongnuo YN560 III and Yongnuo RF-603 trigger (In some cameras you also can fire it remotley using 2 of theese) There is a new model IV. I'm not sure about the diferences.
For TTL there are several models from the same brand ike Yongnuo YN568EX, and you have some options for TTL trigger. The details on the diferent options on TTL triggers are a little out of the scope of the answer. But take a look.
One usefull feature on a ttl flash on the camera is that some models can send a light to aid focusing.
4) If you are going for a speedlight and a wirless remote trigger, your next asset, besides a light difusser for the flash, is... an asistant.
He can provide you directional light, he can light a wedding cuple from 3 meters and you can take a photo from accross 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.
5) The most expensive option is buy a new camera body with a really high iso settings.