For Spanish, I suggest adding both:
http://dle.rae.es/
http://www.wordreference.com/
Reason: For reading literature, a dictionary including advanced words is needed to avoid the annoyance of 'translation not found'. Also, it is very important to include dictionaries that would work for intermediate or advanced reading material. Hence the RAE. I would also add wordreference as I see it as highly accurate and almost indispensible. https://es.thefreedictionary.com/ is another good option that seems to pull from RAE but also includes some bilingual synonyms.