A park cannot survive purely on the income from roller coasters. After guests ride the roller coasters a few times, they'll be too nauseated to ride anymore, and will look for something less intense, which means no income if you have no variety.
One should start by building a conventional park, with a sensible mix of roller coasters, gentle rides, thrill rides, and shops. This ensures a steady income, which in time will give one enough money to build another major roller coaster.
Because you need at least ten types or roller coasters, it is easiest if you build a lot of the compact and cheap ones, like the Virginia Reel and the Steel Wild Mouse coasters. These also work well when they tunnel into the rocks, because of the excitement benefit from underground construction. Try to cram the coasters together as well, as it will also increase the excitement ratings. Later on, if there is still plenty of room, larger roller coasters can be built. Also, to save money, build many launched coasters or reverse-inclined launched shuttle coasters, and make the coasters as short as you possibly can.
A good suggestion for users is to save coaster designs that have a 6.0 rating from previously played scenarios then import them into here. It helps make the game go by quicker and alleviate the need to design coasters on the fly.
This park is no different from all the others. You still need your gentle rides and thrill rides, but in the end, you still need those ten roller coasters.