There are many plants that are edible and many that are poisonous. You won't like what I have to tell you but the easiest source of food is not plants its actually bugs: grasshoppers, ants, almost any insect with the exception of spiders and caterpillars. Make sure to cook your bugs the carry parasites that can harm you so cook them.
Here are some edible plants that are very common in most areas
Chickweed- you'll find this herb in temperate and arctic zones. there is small white flowers on the plant they appear between may and July all parts edible .
Wild asparagus grows in Europe and north Africa west Asia and North America. Wild asparagus has much thinner stalk than the grocery store variety and its great for vitamin c b12
Burdock- this plant has big leaves and purplish thistle like flower heads. this plant is found mostly in western hemisphere. You can eat the leaves boil them twice to kill the bitterness.
Cattail- known as cattails in North America and Reedmace in England found near edges of freshwater wetlands. Most of the cattail is edible focus on washing the mud off and eat the bottom part as a meal the bottom part is white then as a snack eat the top part just like corn on the cob even tastes like corn.
Clovers- lucky for you these are found literally everywhere in grass around trees. Eat raw if boiled tastes bitter.
Chicory- found in Europe and North America and Australia has small blue lavender and white flowers whole plant can be eaten. Pluck the leaves eat em raw and the roots boil them they are tasty.
Seaweed- kelp is found everywhere is water. Its a form of seaweed eat it raw or in soup
And last but not least, plantain- found everywhere good for herbal remedy or as food found in marsh areas
One thing to keep in mind when considering plant consumption, you can tell which plants are poisonous by the milky substance they give when you squeeze there stem.