Do you currently have any other equipment? What do you have?
Boards:
OK so generally a powder board and a park board are different. A powder board is typically longer, with a tapered shape, and a setback stance. A park board is typically shorter, and twin or twin-like in flex and shape. If you want a board that will be good in powder and park, you need to look for a versitile board, rather than an all-out pow or park specific board. Fortunately there are a lot of boards like this on the market (boards like the Burton Custom etc...)
My initial thoughts would lead you to a snowboard with reverse camber. Reverse camber boards are excellent for freestyle, but also excel in powder due to the shape. They float exceptionally well for a board of their size. This way you can get a freestyle/park board that you can ride comfortably in the powder. All the big brands make snowboards which fit into this category.
If you are looking at Burton, check out the Custom V Rocker and the Joystick. The Hero is an awesome freestyle board but definately on the soft side for freeriding. Other options are the Lib Tech Skate Banana, or the Travis Rice BTX. GNU have the Park Pickle. Any many more...
Please read these articles, written by George Cant of Design Cartel:
Board Characteristics and
Board Selection
Have a think about what you really want out of your snowboard, and it will help us narrow down your options.
Bindings:
The main thing you need to think about here is the flex. How soft or stiff do you want them? A softer binding is more forgiving and will let you "play around" more. However you need support and response for harder riding. Unless you want them specifically sorft or stiff for whatever reason, then your best option again is something versitile. Burton, Rome, Ride, Flux, Union, and more all make good bindings offering unique features. Narrow yourself to a couple of brands you would be interested in buying and I will be able to help you narrow down your options. Of course price might also need to be a consideration depending on your budget.
Boots:
Here I'm not going to suggest any specific boot. You really need to try on as many boots as possible and visit an expert bootfitter in person, so they can assess your foot shape and needs. Please read this article I wrote on boot fitting. It will help you understand what you need to thin about and how the boots should feel:
Boot Fitting. Have a read though and it should give you a better idea of what you want/need. If you get back to me on approximate flex (i.e. very soft, soft, mid range, stiff, very stiff) and your budget, I can suggest a whole range of boots you should try on. However, nothing will beat visiting a good store with an experienced boot fitter.
Anyway I hope this helped you a bit. Have a think and get back to us and we can help you further.
