Start with the garden you have.
Spend some time outside before you buy anything. Notice where the sun falls, where the ground stays damp and which spots you actually see from the house. Your first decision can be as small as choosing one corner to improve.
You do not need a perfect plan.
A sketch helps. It is allowed to change. Leave room for plants to grow and for your own taste to change with them.
Expensive tools or rare plants.
Begin with a few useful tools and plants suited to your conditions. An ordinary plant in the right place is more satisfying than a rare one struggling in the wrong place.
A flawless lawn.
Gardens are lived in. A few daisies, a worn path or a patch you have not worked out yet are part of the process.
Every job completed.
Choose one manageable job. Plant something, clear a small area or sit down and observe. You do not have to finish the garden in one free weekend.
Years of knowledge.
You gain those by gardening. Some plants thrive. Others teach you to move them, divide them or try something else. Keep going.