This guide is as simple as the tricks are:

1. As quickly as possible, research the Information Kiosk and Steel Roller-coaster.

Depending on the level you are on and the order at which the research is completed (each level has a set order as to how these are unlocked), ensure that your research is prioritizing shops & stalls as well as rollercoasters until you are able to secure these two assets.

2. Information Kiosk

Sell your umbrellas as the maximum price possible ($20.00) or equivalent. Guests will ALWAYS purchase them when it is raining without complaint. You can easily make up to $4,000.00 over each instance of rain with a park of even just 500 guests.

3. Steel Roller Coaster

The Shuttle Loop and similar designs provide just enough excitement and intensity for many different guests that otherwise do not care for gentle rides.

Compared to other large-scale roller-coasters, the Shuttle Loop is one of the cheapest designs to satisfy these guests at less than $2,000.00.
Instead of building or purchasing a roller coaster that takes up three to five times the space at three to five times the cost, you can instead build three shuttle loops and place them in a fairly compact area, easily charging $2.50 a ride for each one.

This method is spatially aware, cost-effective, and will produce for you far greater gains at a fraction of the cost.
Example:

1 Wooden Coaster = $6-15k, upwards of 250 square feet (or grid squares), with an admission cost between $2.50 and $5.00 pending quality.

3 Shuttle Loops = Less than $6k, roughly 90 square feet not including foot paths. with an admission cost of $2.50 each.

Do you pay 6 grand for a 7.50/guest investment, or 10 grand for a 3.00/guest investment?

This does cheese the game quite easily, so understand the more you work with this trick, the easier the game will feel to beat in most cases. I hope someone out there finds these little tips helpful.