Liccy, there's nothing too far wrong with your setup. Lots of the changes people will suggest are valid opinions, and there are a variety of equally valid opinions even if they are slightly different. Its up to you which ones you take on board.
In my opinion, for an adult pair of levis that tank is a little on the squishy side, but for one adult or a couple of young ones the size is fine. I know these cages are a little squishy to provide lots of accessories without becoming full, but I would suggest another small hide either on top of or halfway ontop of the warm area, and I would suggest a mound of sand in one corner against the wall. In my tank that size I have a mound piled up about 1/3 up the back corner for digging, misted every few days and re-mounded every fortnight.
If the gecko's like the hide you have, keep it. I do suggest another hide or at least the damp sand mound as an option for them too.
I keep mine on the same kind of sand, and all mine have access to a similar waterbowl. They dont use it often, but when they do you'd think they were camels!
If the modo grass is real, potting mix around the roots of it could possibly harbour bacteria and mould and it may have pesticide on it. It's probably ok but you'll get lots of people advising you to take it out. Up to you. When you mist the tank droplets will form on it which the gecko's will like licking off. If it's clean grass then this will be a good thing.
You will also find that it will provie a little food and shelter for crickets before they're eaten. I find that my gecko's can be easily freaked out by crickets touching them when they're not in the mood to hunt, so I put a couple of fake leaves in the tank for the crickets to hide under (and water droplets to form on) so they don't stress the geckos out too much until they're ready to hunt.
I think your remaining gecko will be fine
