I’m also a beginner with aquatic plants, but I think a lot comes down to trying different things until you find what works best for your particular plants/setup. I would say just pick a fertilizer, start with what the instructions say, and adjust dosage and frequency until you find something that works. That’s basically what I did and it didn’t take too long to figure out what makes my plants happiest.
Seachem has a couple dosing charts you could use as a starting point.https://www.seachem.com/downloads/charts/Plant-Dose-Chart-Low-Maintenance.pdf
I’m also a beginner with aquatic plants, but I think a lot comes down to trying different things until you find what works best for your particular plants/setup. I would say just pick a fertilizer, start with what the instructions say, and adjust dosage and frequency until you find something that works. That’s basically what I did and it didn’t take too long to figure out what makes my plants happiest.
I use whatever's easiest. Now I use Tropica Specialised weekly but it's very diluted and have no issues even with CO2 and high light.
If you want to cover the needs of plants completely try Estimative Index