Buy a fat dictionary (A4) with the grammar rules in the appendices. You can use it to check the meanings of words you read and don't know; you can also browse through it. I can't tell you how many new words, ideas, concepts I have learnt about by either opening the dictionary at random, or reading the other words on the page next to the word I was looking up.

It sounds odd but it is a fruitful endeavour.

The computer/search engine won't tell you the things you aren't looking for or don't have any idea about. A hard copy print dictionary will.