I think the best place to start is in your very own kitchen.Take a stroll through your kitchen and see the herbs and spices you normally use.Get a book or go online and look them up.When you have a fair knowledge of the meanings of the herbs you have around the house you can make a charm or if you love cooking go into kitchen witchery(cooking by utilizing each ingredient by understanding it)what I dub magical cooking.
I think if you just follow everyone's advice: research all the herbs you can think of, buy/borrow books about herbalism, and once you think you're comfortable, try and perform a simple spell involving a herb or two. Make sure you really know the properties of that specific plant - and if it's toxic to humans or not! Also, try growing some in your own garden as soon as you can; it will help you feel more at home with them, more comfortable with using them, and you'll have your favourite herbs right at hand if you want to do a spontaneous bit of magick. Happy spellcasting!