50% water changes are for Nature Aquarium Style (ADA) tanks that use Aquasoil Amazonia.
Planted tank, opposite of reef, you want nutrients at all times for the plants to use, namely NPK + Micros. Most people mix their own dry ferts. Digital scale and weigh as you go by EI Index or PPS-Pro.
There is also premixed bottled liquid ferts ("plug n play"), where all you do is push the pump action like a soap bottle.
Then there is auto dosing like in reef, where you can use an auto doser like bubble magus.
But the first question is, would you like to have a low, medium or high light tank?
High light is a lot of maintenance compared to low light, namely frequent trimming, algae removal and control until tank is balanced, diligent CO2 monitoring and adjustment as needed and fert dosing.
For the soil you can simply use Aquasoil, some also add some powders in there like Bacter 100, to build a stable substrate faster. I read some reviews and believe they work.
I also believe in giving a tank the best start and chances to succeed from the beginning, so bring on the powders lol.
Read everything on the internet and then read it again, for specific literature I like Aqua Journal.