For me personally, fruit is the most powerful staple. I know that they are not easily available to everyone - what generally works great in most locations is bananas. They are usually very affordable and readily available year round. Making smoothies with ripe bananas or freezing them for making nicecream out of it is the most common start into this. You can also start by adding some fresh leafy greens to your cooked dinner, cutting down on any non-vegan foods and avoid processed goods to assimilate your taste buds ;)