Pokey Park may seem challenging at first due to its limited size, but it can actually be beaten fairly easily. The key is to maximize your space, that is, build rides that have the most potential to attract guests while taking up as little space as possible. It's a good idea to research thrill rides initially, but don't forget that some guest prefer less intimidating rides. A small, custom built shuttle loop is a great way to attract a large number of guests.
The sloped landscape in Pokey Park allows the designer an opportunity to build many rides underground. This is a good way to maximize space. Don't forget that you can buy a parcel of land on the opposite side of the road. If you choose to expand the park, remember that you are only able to buy construction rights to the land above the road, and it is important to build several footpaths to connect both sections of your park. A Chairlift is useful too, as it doesn't need much space, but attracts guests and boosts your park value. Also, be aware of depreciation (the fact that Park Value slowly goes down over time).
It is possible to beat this scenario without buying any additional land or construction rights, although it is very difficult.
If your park gets too crowded (when guests complain and say "It's too crowded here!"), then start to build paths above the park rides and around the park. This way, guests won't get as unhappy and your park value will stay higher. If all else fails, try to build rides underground and use every square you can. Remember, roller coasters increase the park value faster than smaller rides.
The easiest way to use all the area is to close the park and the rides. Get rid of everything and start flatting it out. Then, start it from scratch, building everything tight and smart. You can put one or two shuttle loop coasters to attract people and have 2 roller coasters underground, now you have 4-5 coasters in your park and it will help your park value.