It's all been said so I'll just throw out my opinion... It sounds like you are starting off right, reading a lot and learning by using M and thinking about the shots. Don't get caught up in the hype of buying so much. It's not necessary.The essence of a good photographer is not what he can do with equipment, it's what he can do without it!
All the fancy stuff does is make it a little easier but you don't learn as much if you can overcome all the challenges with high ISO, fast fps, etc. For example, having a Classic 5D in low light forced me to improve my camera stabilization technique and watch for subject movement. It also eventually made me really appreciate the difference a faster lens makes.
- Don't spend a lot of money now.
Get ONE additional lens of your choice to enjoy at Christmas and learn.
- Learn about the LIGHT.
Flash, Bounce, Diffuse, Available, Off Camera, whatever. Inexpensive triggers would be easy to add. Check out David Hobby's Strobist blog. It rocks for off camera flash info. Read Joe McNally. Lots of great interesting stories about real life challenges and how their experience saved them, not their equipment.
- Build evenly.
Buying a 5D3 is NOT building evenly. This stuff isn't going anywhere. Buy what you need a little at a time and really use it as you buy it. After a year of heavy use, you will really know what you want or need and perhaps you can get a great used 5D3 for less if you still even want it.
- Get protection for your equipment, small things like a monopod and/or tripod, high quality strap and case system with room to grow, etc.
- If you want to experience FF, rent and then perhaps buy a 5D Classic or 5D2 used. What's the rush to spend $3K on a body?EQUIPMENT OVERLOAD
- I can't emphasize this enough... it won't be long before you will experience frustration with too much equipment. I know that sounds hard to believe but eventually you will have trouble choosing which lenses to take, which body works best, should I just take it all?, etc. You'll start having storage issues. It will happen. So don't rush it. I think many here will agree that there is a lot to be said about owning one body and two or three lenses total. The more familiar you are with what you own, the easier it will be to choose how you use it and what you buy next.
I'll repeat - take it slow. Buy used if possible. Sure you can go out and spend $5K on a body and one L lens but I think you will be robbing yourself of a much more interesting experience of slower growth. Enjoy the process and get plenty of books to learn from to maximize your satisfaction and knowledge. There is another thread on here currently that is discussing books. See my post along with others for good suggestions. http://www.canonrumors.com/forum/index.php?topic=11435.0
Have fun and shoot often!!