I'm a beginner, so I wish to make sure buying them is the right call before spending a huge amount of money. I'm having second thoughts because I was told that cambridge history series is generally for people properly trained in historiography and not really friendly for rookies.
The Cambridge History series is a very good set of reference matter, with chapters on a variety of topics that range from synthetic general introductions to definitive (or at least then-definitive) texts on certain specialist topics and periods. However, it's not a good option for the beginner. Firstly, each volume is organised basically the way a historian might want it, in clear thematic and topic-constrained chapters by individual specialist authors, rather than as a single author's continual narrative. Secondly, it is pretty pricey unless you have access via a library. Thirdly, it has been worked on and expanded over the course of more than four decades now, and so its earlier volumes are out of date to varying degrees – the two Late Qing volumes (10 and 11), published in 1978 and 1980, are a mixed bag in terms of historiographical relevance, but the two early to middle Qing volumes (9, parts 1 and 2), published in 2002 and 2016, are largely up to date.
My suggestion would be to look at some volumes that are a little more continuous and a little more recent. Patricia Ebrey's Cambridge Illustrated History of China is somewhat old now (published in 1996, before many key works in revising Qing history which is my specialism), but will be far more digestible than the CHC proper; John King Fairbank and Merle Goldman's China: A New History, Second Enlarged Edition, published in 2006, is also an option though Fairbank (who died in 1991) was already a bit of a historiographical relic by the time of his death; Jonathan Spence's The Search for Modern China, last updated in 2012, is an absolute classic and about the best general intro you can get, but it only covers the late Ming through the twentieth century. Also worth considering is Harvard's History of Imperial China series, consisting of six books by four authors, each covering one or two imperial states in a generally thematically rather than chronologically-arranged format. All are from the mid-late 2000s, so not entirely cutting edge but still pretty good on that front. The six are:
Mark Edward Lewis, The Early Chinese Empires: Qin and Han (2007)
Mark Edward Lewis, China Between Empires: The Northern and Southern Dynasties (2009)
Mark Edward Lewis, China's Cosmopolitan Empire: The Tang Dynasty (2007)
Dieter Kuhn, The Age of Confucian Rule: The Song Transformation of China (2009)
Timothy Brook, The Troubled Empire: China in the Yuan and Ming Dynasties (2010)
William T. Rowe, China's Last Empire: The Great Qing (2009)
Do feel free to ask if you have further questions.