Newb Looking for Simple Answers

I'm new to planted tanks, and I'm just beginning to understand Kelvin ratings. I have a guppy breeding tank - they turned it into one, I never wanted to breed them. It's about 60 gallons, with 2 lights on top. Lots of filters installed. Anyway, the lights are a 4 foot long regular fluorescent light found in any store you shop at. The other light is about 18 inches and has a plant growing light from GE. It's only 3,100 Kelvins, and 15 watts. I know the kelvins is low and already discovered that I should be using about 5,000 to 7,000K. I recently dropped in some water lily bulbs sold at Walmart and they are just starting to sprout. The grow light sits directly above where the bulbs lie in the tank. Lastly, the bottom is covered by standard gravel. My concerns and questions are as follows:

1. My absolute highest concern is the invasion of snails. In my previous setup, snails invaded the tank and literally destroyed the filters. I cannot stress enough that I am looking for ways to prevent snails from getting into my tank. Aside from salting them or using copper or something similar, I concluded that I should be using plants that I can grow from seed or bulb.

2. What are some good low/medium light type of plants that would be good in my setup? I know there's millions of types of plants and I don't particularly care if you suggest bog plants, pond plants, or any truly "non-aquatic" types.

3. I've discovered it's been very difficult to locate online retailers who sell bulbs or seeds. Do you readers out there have any stores you'd like to recommend?

Lastly, I'm trying to keep things simple, low maintenance, and low cost. I am not trying to turn my tank into some beautifully green looking tank like those found on youTube, but instead, my goal is to reduce or eliminate the nitrates that constantly build up since my tank is overpopulated.