as Tinngg suggests, the biggest thing you really need to upgrade is lighting. You will be disgusted and fed up with live plants if you subject them to your amount of light. the play sand is ok. You won't have to dose, just feed the fish to provide nutrients. Platties shouldn't eat your plants.
The amount of lighting determines the need for co2. I think it's best for beginners to stay out of the co2 realm, but probably only because that's how I started. You mention 2x40watt strip lights.
In my experience, the best lighting for a low-tech tank has been 2 sets of fluorescent strips running the length of the tank. Here's what I'm talking about
I don't know if these are 40 watt lights, or what.... but I know that it would not require co2 and would support healthy plant growth.
My only other suggestion is to get LOTS of plants to start, as many different kinds as you can. Java fern/moss, anubias, crypts, swords, ambulia, ludwigia, rotala, etc. Then see which ones grow best in your tank and keep 'em!
Oh yea, and read rex's guide. All of it!