I would stick to Canon Both nikon and Canon Are great but Value for money the canon will come through.

Buy the right lens to start with and you will have them for years.
No point wasting money on what people call a Starting Learning lens, becuase u wont get the true capabilitys of what you can produce and have to buy a better one later anyway.

Stick to f2.8 and L series lens and they will be by your side for years to come and you can just upgrade body.

I would go for a 5d or 5d mk2 stright off. Dont waste your time going anything less if you plan on doing weddings and gigs like you mentioned. Becuase they wont perform in low light and you just spending money for nothing.

Get the best of what you can afford and play with it with in 6 months you will be shooting events and all.

on another note I woudlnt wait for people to upgrade Becuase if you buy the right lens to start with you dont need to upgrade.

I would recomend

24-70 F2.8 L about $2000
70-200 F2.8 IS L about $2700

a 580ex II Flash $550

and a good Tripod $200-350 mark

You can pick up a 5D for $1800 or there abouts now days.
and a mk2 for about $3900.

Think of it all as a investment though.

I Have bought other lens before cheaper ones and then regret it becuase they dont perform how i need them to So I have learnt to get the right stuff from the start now. Lens specially.