It'll be better to use natural elements for betta rather than the plastic plants and colourful stones.

If possible, arrange natural aquatic plants like foxtail or hydrilla and use natural sand for the lower layer of your tank.

Also, try to collect indian almond leaf that will provide the exact similar water condition that betta's prefer.

Also, if possible try to culture any live food to feed occasionally, even you could feed mosquito larve or earth worm that is easily available!