I went there three weeks ago and made 180 Ks around over two days. The first day barely managed to pull 100.
100 Kms / day is feasible. 200 in a day is very unlikely, especially given the very soft nature of the sand there and the steeps climbs that will produce many refusals.
Also is important to be clear about the potential damage to the bumpers. Both approach and departure angles are important to avoid damaging your car.
Regarding the gas, I used a full tank + 45 lt in three rotopax jerry cans and finished with 1/4 tank. I have a 2 doors JK lifted with big tires, which makes me burn gas like hell. So, depending on your car and driving style it might be required the equivalent of another gas tank.
Liwa is an amazing experience, not only because of the extremely beautiful terrain, but especially because it will challenge you (nerves, resolution, skills, teamwork to rescue team members on difficult stuck situations), and also the cars itself. I have gone twice and never get enough of it.
If you love off-roading and have the skills and the right car, it is something you need to do.