I'm planning to set up a 29G planted tank. I'm just going about it slowly.
Have you decided what kind of substrate you'd like to use? I'm going with Eco-Complete topped by black gravel.
Do you know what type of wattage you'll be using in your bulbs? I'm looking at using at least a 55W, but probably not more than a 65W, bulb on mine. This will determine what plants can thrive in your tank.
Will you be pumping in CO2? How complex a system do you wish it to be?
Are you going to raise fry? If so, think about getting plants among which the fry can hide.
Lots to think about here!
PS - I think you'll be pretty stocked with your platies and mollies. I would think twice about adding any gouramis.