This really depends on your use cases. If you use this for browsing, reading documents and slides, watching videos, 8GB ram would be more than enough. For the storage, 256GB would be also good as well. However, if you find yourself often build up a pile of documents or files in laptops, it would be better to get 512 since you'll get less fussy about it. I've got my Macbook in Ebay, there is another website which is backmarket.co.uk would be risk free when compare to Ebay.
This is quite a beefy laptop as well, apart from studying, I use it for video editing and music productions and the processing power is sufficient.
Hope this helps!