Well, I would say to go for a biotope since what's better than what nature has already made? but that would mean that you would have to choose between an Indian biotope (for the gourami and danio) or an Amazonian biotope (for the tetra) but since you have 2 Indian fish vs 1 Amazonian fish I will tell you about an Indian biotope.
Ok so for starters you can use either a dark or light substrate that's up to you, for lighting use a medium-strong white light, use lots of branches and some large rocks and a few pebbles, it should have a little surface agitation but not that much since the water should be mainly stagnant, use Indian almond leaves and mulberry leaves as the leaf litter (they like leaf litter and they benefit from tannins also their benefits are far greater than any disadvantages you may think of) since it should be a black water tank, as for plants you have a lot to choose from! you can use different species of cryptocoryne for the foreground and midground, also for midground, you can use rotala rotundifolia and rotala macrandra, Utricularia Auria would be an interesting plant since it is a carnivorous plant that eats small things like daphnia or ostracods, as for the background you can use Cabomba caroliniana, Limnophila indica, another good choice would be Nymphoides krishnakesara or Nymphoides indica since they are dwarf water Lilies, and that also takes us to floaters and I recommend you 2 floaters, 1. Salvinia nattans, 2. Ludwigia sedoides, and las as epiphytes I would recommend Indian fern. As for the general layout that is up to you but just remember that the gourami and the tetra feel safer in an aquarium with diffused lights and cover up-top and the best way to archive this is with water lilies and floaters. And at last, we shall talk about parameters: temperature 24-26 degrees celsius, Ph 6.5-7.5 and Gh of 90-200 ppm.
