1. Buy a castle. Pots can be both expensive and inconvenient. I started out it pots and they took up too much space. Plant one garden on one side then another on the far side. This will let you separate plants that don't like each other.
2. If you want to gain a lot of gardening ranks faster and for less money. Get to level 2 gardener, then when you get to Krok buy the level 2 spells. Don't spend any money on seeds because Kroks give Pink Dandelions.
3. Think Smarter. For small plots there is a great way to cast level 2 spells that cover all the plants. Put one plot in the center and put one North South East and West as close as you can. See diagram. This will allow you to save Power and grow more plants. Level 2 spells cover a good sized area, but are only efficient if you can cast on 3 or more plants. This diagram lets you cast on all 5 plants.
Diagram. ___X _X X X ___X
4. Picking your Plants. One of the most important parts of gardening is picking the right plants for what you want. If your interested in getting Experience and Crafting supplies I recommend Pink Dandelions. They are easy to care for and give a variety of Crafting items such as Bloodmoss, Black Pearls, Crystal Vials, lava lily, springs and ancient scrolls. They also give a small amount of gold and regular dandelion seeds. If your interested in Cards and Gold I recommend Stinkweed. They give treasure cards like Poison and Smokescreen. They are more difficult to grow and you will need at least rank 2 pest spell.
5. Golden opportunity. So if you don't need the crafting items or cards you can sell them. Black Pearls alone are worth 100g each. Once you have level 2 you can always go to Krok and get more Pink Dandelions. The gold can be unlimited.
6. Don't overdo it. In other words don't plant 40 plants and expect to keep them all alive. I recommend you start with 4 or 5 then once you have level 2 skills you should be able to handle 10 or 15 at once if you follow my diagram.
7. Forget Me Nots. Juggling plants in the game can be difficult. I find it necessary to check them once in the morning and once in the evening. If you let them go too long they start dying. You don't have to spend hours playing, just log in and provide care and log out.
8. Don't forget to play. Having a garden is both fun and rewarding, but don't forget the higher you get in the game the more neat plants and spells you will get to work with. Don't neglect your characters progression. The better the character the better the garden.