Read as much as you can. Try to understand words in context. Remember there is no royal road and no shortcut to success unless you involve yourself seriously if you want to learn. Just do it as little as five words per day and you shall see the big difference. The more reading habit the better, and you will develop a sense of grasping meanings, connotations, figurative and idiomatic use of the words. This will give you insight into language. It will rather be more useful if you note few words and use them in your speech and write them quite often.
Rule ONE: Read and try to understand meanings in context

Watch English movies. Sometimes a book you are reading maybe old and the words are either obsolete in giving the same meanings or they are colloquial. If you read victorian novels like Tess of the D’Urbervilles, Emma Woodhouse or Wuthering Heights you will see many words out of date. Tess is called “fine figure of fun” and this looks as if she is funny, but the context says otherwise. Similarly the words and phrases like gay, green malt on the floor, stubbard-tree etc are either obsolete, colloquial or their meanings and connotations got changed. So it is advisable to be in touch with the modern language and movies is the best options. In movies many times you see the dialogues are presented written on the bottom of the screen and if you can’t understand a character’s speech you can read it. This is very helpful because expressions are well understood in live situation. You read or listen to the dialogues and see the situation at the same time. In this way you understand expressions even without dictionary. Suppose someone says “Oh! I forgot my ring on the window ledge” and picks it up from the ledge now here you have seen the ledge and therefore you have understood what it means. Remember such understandings are long lasting. You never forget what you saw. Once I was teaching Wuthering Heights and I was looking for the meaning of tankerd and I still remember its meanings when even years elapsed even to an extent that I think I can’t forget it. Do you know why? I just opened google images and saw the image of tankerd.

Once I was watching Mind Your Language, a British sitcom, and Mr. Brown (a language teacher) made embarrassing mistake and was pointed out by his student Ali Nadeem saying “You have dropped a clanger”. Now I understood at once what drop a clanger means even without the help of any dictionary because I was seeing the situation at the same time. So the rule TWO is;
Rule TWO: Watch movies and consult Google images

Try to learn roots. Once you do it there are thousands of words that even in first look shall be intelligible to you. Suppose Greek misos means hatred and anthropos stands for man, so the word misanthrope is easy for you to guess. Similarly the words like; philanthropy and philanthropic are not Greek to you.The word gynecology is known to you as a treatment of woman (gyne) and what if I use the word misogyny having in mind the meanings of misos and gyne. Yes you are right it means hating women. For roots I highly recommend you must read Word Power Made Easy by Norman Lewis. It’s the best book I have ever seen.
Rule THREE: Learn roots

Try reading stories first, because stories contain narration which is always a simple thing to understand and once you grasp the situation there is much to know in context. It is important to develop a competence to understand the meanings in context. That will make you use to with it and you will be able to use those words in your speech with skill and preciseness. Reading essay is the later stage and go for that once your abilities in reading stories get mature.
Rule FOUR: Read stories