How to add wordpress plugins in along with my standalone theme

You can use TGM Plugin Activation library to let the user know about required and recommended plguins that your theme depends on.

Automatically installing plugins is not a better choice instead let the users know that X plugin should be installed and activated in order for the theme to work properly.

If your theme requires a plugin without which it gives error then make sure to add checks for functions like so:

if(function_exists('xplugin_function')){
   //code
}