"LSI" is a way to help google understand the context of your article, remember google spiders can see the keyword 'apple' but apple can mean the brand or it can mean the fruit. So you need a way to help the spider understand fully what you're speaking about and the context you are speaking in, you do this by using 'lsi', so it's not really a set of words but just to help and ensure google can identify what you're talking about. So 'iphone', 'mobile', 'cellphone', 'telecoms' anything to suggest you're referring to the mobile brand rather than the fruit could be classified as a LSI. While for the fruit, 'nutrients', 'sweet', 'fruit', 'banana', anything to suggest similarities to a fruit would then have google classify your article by the 'LSI' and understand you're speaking of fruits.
Write naturally, spread around phrases that are commonly used when speaking of the topic.