if you're looking for more games similar to moon and x, i would recommend omegaruby/alphasapphire. they're remakes of ruby and sapphire for the gameboy advance, with elements of emerald (basically an ultimate version of ruby/sapphire) thrown into the mix so that it feels more like a remake of the three. there are some fun features to play around with in oras that aren't in xy (dexnav, secret bases, soaring) that i think are super neat and underrated in the franchise. black/white are also amazing games to play if you're looking for a pokemon game with better story, though i do think they're more difficult than moon and x, so if you're looking for a better challenge, they're a good route to take.
and if you're feeling like getting acquainted with the games where pokemon started, you can check the 3DS eshop for red, blue, yellow, gold, silver, and crystal. they're not everyone's cup of tea, but if you don't mind older games or are just curious about how pokemon played back in the day, they're relatively cheap and worth the download. plus, you can transfer your pokemon from the eshop downloads and send them to your x and moon. it's neat to have pokemon from such old games in their nice new 3d models in gen 6 and 7.
overall though, i think any pokemon game you decide to check out will be worth the money and effort. they're all really great games and while not everything is always in my taste, i can't say i've ever played a pokemon game and didn't have a good time.