One of the first things you should do is remove the walkways on the walls and inside the castle, as it will both prevent guests from getting lost and get you about $4,000. After that, start building your rides: A gentle ride near the entrance, a small roller coaster like a Wooden Crazy Rodent Roller Coaster, and some more gentle and thrill rides inside the small, enclosed area. After that, add some stalls. You have plenty of roller coasters available from the start, so you might want to stop researching roller coasters for the beginning.
The main difficulty is the terrain. There are quite a few hills, so you have to plan your paths and rides accordingly, a good strategy is circling the hills in the middle by rides, and in the end, make a coaster (probably a Vertical) above all your rides.The guests in this scenario are pretty rich ($65 - $95), so you can set your entry fee higher than in previous scenarios. Start out with $30, and increase it over time up to $50 or even $55. Build new roller coasters along the hills and try to squeeze smaller rides between them. You need quite a few exciting roller coasters to attract all the required guests. Remember that marketing can get you a few more guests near the end.