Lots of plants or not, this tank is already looking good.. And welcome to the forum!
You mentioned traditional gardening. If you already have experience in that, you may know that plants require three major nutrients, which we call "macros": nitrogen (aka nitrate or N), phosphorus (aka phosphate or P), and potassium (aka K).
And they require a host of minor nutrients, the "micros". They're like vitamins. Iron is the most important one, so it is often treated separately; but when someone says micros, they usually mean the whole list, including iron.
One of the micros, copper (Cu) is necessary in small amount, but toxic to aquatic life in the larger quantities found in terrestrial fertilizers. And the nitrogen in terrestrial fertilizers is usually in some form of ammonia, which is toxic to fish. So these fertilizers can only be used with great care, best to avoid them for now and stick with aquatic ferts.
And then plants also need carbon, typically from CO2. If you do not already have one, get a drop checker and 4DKH solution, to help you monitor CO2 levels; they're inexpensive and well worth it. DIY CO2 is a bit of work and recurring expense for this size of a tank, and I'm sure you'll get recommendations to switch to pressurized. But don't let anyone make you feel rushed here, DIY is fine for now. When you're adding CO2, it needs help to travel around the tank and touch the leaves, where it can be absorbed and actually useful; and this requires more water flow than a normal freshwater tank. Multiply your gallons by ten, and that's a good guideline for how many gallons per hour (GPH) you need. It can be achieved by any combination of filters and powerheads, and should reach every part of the tank, so that all plants are gently swaying in the current.
And finally, light. I'm afraid I cannot estimate your light intensity, perhaps someone else can help with that.
You mentioned Excel. Seachem has a whole line of ferts. Here are the applicable ones:
Flourish (with nothing after it): Contains micros, including iron.
Flourish Excel: This is what you specifically mentioned. Contains glutaraldehyde, which plants can use as a minor, alternate source of carbon. You have real CO2 which works far better, so no need for this. Some plants will melt or be killed by Excel, unless it's introduce very gradually. Your vals and anacharis are on this list.
Flourish Nitrogen, Phosphorus, Potassium: Three different products covering the three macros.
Flourish Comprehensive: Like plain Flourish (micros), with a trace of macros, but too small to be useful.
There are also dry aquatic ferts. Which are a LOT cheaper than any liquid fert in the long run. You can even make your own batches of liquid ferts from them.
Finally, you'll need to decide on a dosing scheme. You can:
1) Dose much more than is needed, so no plant will go hungry for any nutrient. Then perform a 50% water change each week, which keeps the excess from building up. This is referred to as Estimative Index (EI).
2) Dose exactly what is needed, or slightly more. This reduces the need for regular or large water changes, because there's less buildup. But it's a bit trickier - you may under or over estimate what plants need.
These are broad scheme classes. There are endless variations.
And this whole post is by no means comprehensive. Just a little primer for you that touches on all the relevant topics, which will certainly lead into more specific questions and answers.