So over all, Co2 is not worth it, and I will have better luck with Liquid Ferts?
Some explanation is clearly needed. First, the most important factor in aquarium plants is the light. Light drives photosynthesis, which is how plants grow, and every species has a minimum requirement for light intensity. There is also spectrum, because photosynthesis requires both red and blue light only, but adding green to this mix improves plant growth. Without adequate light in both intensity and spectrum, the plants will struggle or fail.
Once the light is sorted out, plants need 17 nutrients to photosynthesize. Some of these are macro, others are micro. Nutrients occur in most aquaria from the fish being fed, and water changes. This may be sufficient for some plants, if it balances the light and both are suited to the plant species.
Within this balance of light/nutrients is what we term Liebig's Law of Minimum. This is a principle developed in agricultural science by Carl Sprengel (1828) and later popularized by Justus von Liebig. It states that plant growth is dictated not by total resources available, but by the scarcest resource (limiting factor). So in the aquarium, if say calcium was insufficient for the needs of the specific plant species, and everything else was available including adequate light, the minimal calcium would slow photosynthesis in the plants.
So getting the balance is important, not only to provide everything the plants need, but to prevent nuisance algae. Algae, unlike higher plants, can take advantage of any imbalance. This is why too much light (intensity, or duration, either individually or both), wrong spectrum, too much fertilizer or not enough fertilizer, can all affect the balance and cause algae problems.
The GH of the source water is the major source of calcium and magnesium, so this needs to be known. Fish food provides pretty much everything else, depending upon the fish load, feeding, and plant species [remember, some need more, some less]. In most cases a comprehensive fertilizer will provide sufficient supplementation. But it has to be a complete balanced fertilizer, because too much of one nutrient can cause plants to slow assimilation of other nutrients. Floating plants and those not rooted in the substrate benefit from a comprehensive liquid. Some substrate plants can benefit more from substrate tabs, depending upon the plant species.