俺倒是有个字典...

I have an OXFORD ADVANCED LEARNER’S ENGLISH DICTIONARY.

There are bunch of notes which are used for the word entries. (Maybe most of dictionaries have this kind of notes)

e.g.
Dated -陈旧的
Derog (derogatory)- 贬义的
Dialect -方言的
Euph (euphemistic) -婉转语
Taboo -避讳
Ironic -讽刺
Joc-jocular -戏谑
Offensive -轻蔑

This can help you avoid accidentally using some “bad” words, but the subtlety between words, especially between synonyms, (“inexpensive”, “cheap”, or “a good bargain”) as you have said, you have to learn and tell from the context when you converse with native speakers. No dictionary can help you to this fine grained level. You got to be that dictionary yourself. :)