The only golden rule of language learning is to enjoy what we are doing! Auguri!
Ah yes, I know those frequency lists. The one for Russian isn’t brilliant, which was why I was hoping you’d found a better placto find them 
I like lists. The Magic number seems to be the most common 2 000 words in any language; once you know them you can consider yourself to have a good working vocabulary. To read a book and understand it, of course you need a few thousand more words. I’m going through the Harry Potter books in Russian, and there are a lot of Quidditch terms to learn
I have I 5000 word frequency list in Italian which i did not find from Wiktionary, I don’t remember where I got it though. I’m sure I just googled “Italian Frequency List” and dug through the links until I found a good one. Sorry about not presenting a more specific method.
The lists do not have to be scientific. If you go through and save the ones you need, you can upgrade your “known word” number in a hurry and that has many benefits at LingQ. On the other hand you may need to create better captured phrases at some point.
The interest in reducing quickly a number of the “unknown” words, which are actually the words known to the user, emerges again and again in the Forum. The most recent is:
Steve and Jeff, I understand the advantages of saving each form of a word as a separate “knew” word (for a beginner in, say, Russian, for studying suffixes etc). However, there are too many situations in which doing so creates disadvantage. LingQ, IMO, could have suggested, as an option, the possibility to decrease the number of the “known” words automatically. In case of e.g. English, it can be done (and especially make sense to do ) by scanning the tables of the word families and combining all the “unknown” words of the same family into one. It is easy to do using, say Paul Nations tables, which had been also discussed in this forum and Steve’s blog. This is what I do in developing my player, in which quick understanding of the meaning of the subtitles is more important then studying the word suffixes.
We are not about to change this. I am sure there are arguments for and against.