you don't have to have a 'green thumb' to grow a garden
I hear so many people saying things along the lines of "I wish I could grow a garden, but I don't have a green thumb." In reality, you can be a terrible gardener (like me) but still grow a garden.
To get started, I recommend getting a small planter or a large enough pot to grow a couple different types of plants, enough soil for your container, and a few bags of seeds that catch your eye (optional: some type of 'flower food'). Fill your container with soil and follow the instructions on the back of the seed packet to plant them.
The reason why I suggest growing seeds instead of buying already grown plants is that seed packets are (relatively) cheap and come with far more seeds than you need for a plant. If your plant dies, don't be discouraged. Just remove it and plant new seeds in its place.
After a while gardening, you will begin to develop your skills. Eventually, you will have a green thumb, because it is a skill not a natural talent.
in my garden
In my actual garden, three of my plants have died, so in their place, I grabbed a couple of seeds from my collection (Marigolds, Zinnias, and Alyssum) and planted them. In a few weeks, I should have a few plants that will take their place.