There are usually multiple strategies to successfully completing a scenario; these can be discussed in the comments below, written down in an additional section of the article or added to an existing subsection.
Start off the park by building a few flat gentle and thrill rides, and one cheap roller coaster. Also, raise the entry fee to $25 and get rid of the extra paths. Don't bother buying more land at all, because the amount given is about 50 times bigger than the amount needed. Throughout the scenario, just slowly add rides. The objective is not difficult at all. In fact, this park is easier than Victoria Falls.