If you are going witha community tank, platys (or is that platies? The singular form is "platy." are awesome. They now come in many colors; I just picked up a nice blue guy and he really adds a lot to the tank.
I would go with whatever color gravel you fancy; I myslf prefer more naturalistic colors such as browns and tans tat would be found in a stream. Plants, again are your preference. I use artificial, realistic greens and reds personally.
To start, I would only put one or two smaller fish in, have your filter running and your heater and temps good before doing so, and let the tank cycle; trowing a bunch in will lead to an ammonia/waste spike. You need to give the beneficial bacteria time to set itself up and grow in your filtr's cartridge as well as in your gravel. One helpful tip is to try and get a handful of gravel from someone else's healthy, established tank; it will speed this up.
Anymore questions, please ask. I can talk tanks all day.