This guide to getting a good start on the Magic Plants was written by Jazzo, with help from sfrose.

PT Getting Started Guide MAJOR SPOILERS
Don't Read Unless You Want to Spoil the Beginning of the Game, By: Jazzo

While reading this guide, you must be familiar with the following terms:
Prepare a pot: Put soil and water in.
Self-pollinate: Drag a mature plant's pollen onto itself.
X-Pollinate: (Cross pollinate) Drag a mature plant's pollen onto another mature plant.

Getting started. First off, prepare eight more pots, plant all the seeds in your seed tray and all the ones in seed storage. Next, make sure your game speed is set to "Fast" then use both doses of your insta-grow vaporbomb (The purple Vial) Now you are ready to start.

It's nice to start out with one of the six magic plants, and there are two magic plants that are good money-makers. They can both be bred from the starting plants usually and can survive to mature in the basic soil level. They are the Rosaceae Fern and the Fourpetal Maple. They can be bred with the following combinations.

You can get Fourpetal by X-Pollinating the following flowers:
Citrus + Jalapa
Fourpetal + Fourpetal
There are many other combinations but they will not be found in the starting plants.
You can get a maple by X-Pollinating the following types of foliage:
Ball Cactus + Maranta
Maple + Maple
There are many other combinations but they will not be found in the starting plants.
sfrose gave me some examples of breeds that get a fourpetal maple, also, this should help you understand the above:
Citrus Ball Cactus x Jalapa Maranta
Jalapa Ball Cactus x Citrus Maranta
Citrus Maple x Jalapa Maple
Fourpetal Ball Cactus x Fourpetal Maranta This is if your confused, so I hope you get now how it works.

You can get Rosaceae by X-Pollinating the following flowers:
Fourpetal + Spotted
Bluestar + Jalapa
Rosaceae + Rosaceae
There are many other combinations but they will not be found in the starting plants.
You can get a fern by X-Pollinating the following types of foliage:
Maple + Reptans
Astera + Maranta
Fern + Fern
There are many other combinations but they will not be found in the starting plants.
This means if you breed two types of flowers that make Rosaceae and two types of foliage that make Fern, you'll get a Rosaceae Fern.
Put it together to find two plants that can be x-pollinated to make a fourpetal maple and a rosaceae fern.
The Fourpetal maple should survive fine in the starting soil, but the Rosaceae fern will not survive as long so make sure to self-pollinate and sell it quickly. Keep seeds for the other plants and keep selling these two magic plants until you can buy the second level of soil (blue.) After that, there is another MP (Magic plant) you can start looking for. That is the fabled lemonbush. It will have a little bit of trouble surviving in the second soil level, but it will survive long enough. It also can sell for $436. You can get a fabled flower by x-pollinating the following flowers, some of which you might not have:
Citrus + Daisy
Venomous + Bluestar
Fourpetal + Rosaceae
Fragrant + Jalapa
Fabled + Fabled
If you don't have any of these, play around with x-pollinating.
You can get a lemonbush with the following combos:
Ball Cactus + Astera
Pipe Cactus + Fern
Maple + Maranta
Lemonbush + Lemonbush
Once you have that, keep making it and selling it until you can buy level 3 soil. Then, keep x-pollinating as you which, because in the gold soil, all plants will survive. The last three MPs are Nox Orchid, Aureus Scandens, and Mela Rare Oak. Also, keep making money to buy higher levels of water, shears, net, and more seed boxes. I usually buy upgrades in this order:
L2 Soil
L3 Soil
2nd Seed Box
L2 Water
L2 Net
3rd Seed Box
L2 Shears
L3 Water
L3 Net
L3 Shears
Keep x-pollinating and try to find as many interesting species as possible. I hope you're off to a good start!