Lighting is fine. Not using CO2 will limit your foreground idea since carbon is a major component to photosynthesis. There are DIY ways of at least doing some carbon supplement (there are recipes here for it). This is also limiting and not controllable, but maybe you can give it a shot.
"Lush foreground" is a project. It demands a lot of attention and understanding of what plants need to grow to a healthy lush form. I recommend reading up on this forum in some other journals to get a better handle on the fertilizers and plant needs. There is a book you can get here (look at top bar on right, "Planted Tank Guide"). This was written by one of the staff here years ago and its a pretty good intro guide to get you a general understanding of what is needed.
As far as substrates, black diamond sand is inert. There is nothing wrong with using it, but it is not providing any nutrients to the plants. You will need to supplemental dose the water column in order for the plants to get the nutrients they need. You can however add to the substrate to give it some goods. There are tons of ways to do it, root tabs, or using an organic topsoil as a base, or even mineralizing your own topsoil. You will need to do some research on all of this, its all here.
The worst thing you can do is rush and set this up and dump money at plants that will not survive. Get the basics down go from there.