To make quick money, catch every butterfly you see. If you catch ones you already had, you get money. Not much -- But it adds up.
If a plant is sick, save your money and throw it away instead of buying spray. Unless it's your only one. It saves money.
Don't use all your money on expensive growth hormones. Instead, put the game on the fastest speed. You save money, and plants mature within an hour.
Because this game is done in real time. If you move you computer clock ahead, you will reduce the growth time of you plants.