Many of your course textbooks can be found at the University Library free of charge, so check out the library before using your funds for textbooks.
This small dictionary offers the most accurate and up-to-date coverage of essential, everyday vocabulary with over 90,000 words, phrases, and definitions based on evidence from the Oxford English Corpus, a unique databank comprising hundreds of millions of words of English. Definitions are easy to understand, given in a clear, simple style, and avoiding technical language.