There are tons of ways to go and very few are totally wrong for all, nor are any of them totally right for all. SO what works will depend much on what else is going in the tank and what you want. Big sturdy plants that will grow in anything or fussy small plants that are more difficult? Do you have a specific idea or just working into it and need to see what works for you?
It can get down to personal things like why the will to do plants. I put the plants in to make the fish look better and I want large fish who do not do well with tiny so I am more inclined to simply add most anything on the bottom and use plants that do fine in that. Nothing real fussy needed and it all gets mixed after some time of digging, moving and sorting. Does the tank get built and stay as such for longer or does it go through change almost daily/weekly?
Do you favor a solid, one color, one type bottom like found at a beach or do you favor a more diverse, mixed bag like seen in rivers and creeks?
These are some things that only you can known and it does pay to think in the way that suits you personally. In my case, I often do simple and add a bit more of whatever feels right and let it all mix as my plants don't care and my mind looks for the mixed river/creek look.