Hi & welcome to APC
A 30G is plenty big enough for your first tank. You have some good ideas & plans. The first & most important thing is your lighting, which is often over looked. A 65 watt fixture with a 6700K bulb would give you a low-medium light setup.
You would be able to grow a variety of plants. A easy to maintain background plant, that I like very much is Crypt crispatula.
With over 2 wpg you will need a source of C02 injection, DIY would work fine along with the addition of Seachem Excel. You would also need to add fertilizers:nitrates,phosphates. potassium & micros.
I think brown substrates make a natural looking tank. You could go with Flourite dark or red. Pool filter sand is another option. As for black sand Seachem as a new product out that works nicely.