You'll have to build as much compact as possible, because, obviously, the park is pretty little. There's land available to buy, but it's really expensive ($90 per tile), so you really shouldn't worry about expanding your park before you've covered your initial space. As a matter of fact you can beat this scenario with no problem at all without even purchasing any extra land. Later on you'll have more money so that you can buy more land if you like but it shouldn't be extremely necessary.
Also, another big trouble this scenario has to offer you is that it rains really a lot here. So building underground and building indoor rides (such as Haunted House or 3D Cinema) is a good thing to keep in mind. You should've already noticed that most of your guests won't go on your rides when it's raining. In parks like this where it rains a lot, this can be a big issue because of your temporary income. As it rains a lot, you might charge more for umbrellas and build many Information Kiosks.
Flat rides like Haunted House, 3D Cinema, Bumper Cars and Motion Simulator are rain-proof and will not be affected when it rains, so make sure you have built all of these kind of rides. As for tracked rides, you don't have to build them completely underground in order to make them rain-proof, but they need to have most of their sections underground. Of course, you don't have to build everything rain-proof (and it would be very hard to do), but remember that your loss of income in rainy days will be somewhat eased if you have one or two coasters or larger tracked rides underground.
A reasonable option when building some of your coasters is to build them in powered launch mode or reverse-inclined circuit mode because even though they usually don't have a very high Excitement Rating, they can be built short and become good money-makers and attract more guests. But of course you should build at least one larger coaster to be your main source of income.
At the beginning you should focus on building some thrill and gentle rides and a small roller coaster (preferably a cheap one such as the Steel Mini). Keep on slowly expanding your infrastructure in so far as you research new rides. You should keep the strategy used for earlier scenarios, but not forgetting to build compact and underground whenever possible.
Three years should be plenty of time to get the 800 guests demanded. If somehow you need more guests in your park at the end of Year 3, make use of marketing campaigns, although it shouldn't be necessary at all, as usual.