Betta are a great beginner fish, wonderful in their own right, and adaptable enough for a beginner keep easily and to enjoy. I respect your desire to go slow and learn about keeping fish. You might even consider putting a single Betta into a 5g or10g tank to make it easier to learn about aquarium maintenance and fishkeeping.
But with a >50g tank, you eventually may want to get more deeply involved in the hobby. I suggest you ask your question here. You'll get a whole different perspective.
Beginner Freshwater Aquarium
This is the main freshwater section of Tropical Fish Keeping (TFK), the parent site that this Betta forum is a subsection of.
For your plant questions there is a plant section on this (Betta) forum, or you can go here: Beginner Planted Aquarium
Welcome to the forum.