To keep plants healthy there are 3 basic needs - light, co2, and nutrients - that need to be balanced. How much you have of one, affects how much you need of another. I didn't see any mention of co2 in your post, so I assume you are not planning on adding any. If so, then lower light is probably better. Too much light would lead to an imbalance and then you get algae.
As far as the nutrients go, all plants need Nitrogen, Potassium, Phosophorous (generally referred to as the "Macro" nutrients), and then smaller amounts of other trace elements (referred to as "Micro" nutrients). You will get small amounts of the Macros from fish food and waste, but generally it is not enough to keep the plants happy. There are many ways to add these nutrients, with lots of different products out there. There are pre-mixed solutions that make it pretty easy, but these are generally more costly. I think most will agree that buying dry fertilizers is the way to go. You can buy large amounts for very little money. The most common ones would be Potassium Nitrate (KNO3) and MonoPotassium Phosphate (KH2PO4). A combination of these two will cover all of the Macro nutrients. For Micros there are a number of products as well. The most widely used is probably CSM+B. Again it is relatively cheap in large quantities.
Now, how much to use gets a little harder. This will depend on your tank size, plant density, lighting and co2. There are serveral methods used to help get you in the right ballpark though. The Estimative Index method (EI) is probably the easiest and most common. You should be able to do some searches and find lots of information on it. I also find the Nutrient dosing calculator on Rotala Butterfly | Planted Aquarium Calculators & Information
to be very helpful with this.
Obviously there is a lot of information and some differing opinions out there. It can be quite overwhelming. But hopefully this gets you started in the right direction. And hopefully others with more knowledge and experience than me will chime in and help you out too.