If you are going to get serious about video, a good camera is a nice investment -- although these days you don't really have to spend a lot. You used need hundreds of dollars, now you can get a nice HD cam for $150 to $200 -- or maybe even less.
I like the premium theme idea. I think premium themes give you better support and stability than free ones. I've heard too many people get messed up with their free themes when WordPress makes an update. If you are going to go free, at least use one of the WordPress default themes like Twenty Eleven/Twelve, etc. As you know I'm a big fan of Genesis.
Before you buy a forum script, are you sure you have the traffic to support it yet? There is no specific amount (and it varies per site.) For example I had WAY less traffic to my hair site to get that forum going because it's so niche. For this forum I needed more.
I have never bought a vBulletin mod except VBSEO. Be careful of using too many of these unless they are supported by vBulletin. A lot of mods have security risks. I used VBSEO for years but had a host of hacking issues due to holes in the script and I uninstalled it. I try to keep my mods to a minimum.
If you want to dip your toes into paid advertising, I would start with Facebook. The ads are much cheaper than say Google AdWords and you can go very, very, very targeted because FB collects so much info about people.
I wouldn't spend it all. Save some for your bank account too.
Just my 2 cents.