A first essential is enthusiasm and an interest in plants, flowers and growing things. You are reading this so you qualify on this first essential.
Know that plants require air, water and a safe home – (soil, plant pot or bit of land).
Seed or plant matter to start life then nourishment to continue living. Even without a gardener’s help bare soil will be colonised, mainly by unwanted weeds in my case.
Size ins’t important you can start to garden on a windowsill or in a plant pot.
I recommend some instant gratification, try acquiring a mature flowering plant or good vegetable seedlings to get you in the mood.