If you are shooting in a small studio, then you are going to find that the 70-200 or 70-300 is going to make it difficult to shoot full length shots. Keep in mind that these lens behave as 112 on the short end so that will be a limiting factor. I personally often use the Sigma 18-125 for studio work just because it gives me the ability to shoot from full lengths to head shots with one lens from one position.
Here is an example shot with the Sigma lens:
Re: What to get with a 00 budget
As for lighting, I would not recommend making a large investment in multiple shoe mount type strobes. The 420 ex is adequate for portable work such as weddings and events. I have shot many weddings with the 420EX and it worked well. Keep in mind that when shooting the formal wedding shots that you're much better off with studio lighting (I use 4 Novatron heads in large umbrellas for the posed wedding shots and I've used the same setup for 30 years now). Now days you can get some real bargains with kits from Alien Bee for example.
Here's a poster type shot made with an Alien Bee setup:
Re: What to get with a 00 budget
Cheers,
rfs