Grammar
Grammar study is a recurring subject of controversy. Some say to ignore it completely; others say to go all in.
A personal observation is that, coincidentally, people who like grammar tend to think of grammar study as very important, and people who don’t like grammar tend to believe that it doesn’t matter. So, a piece of prudent advice to start with would be this: don’t approach grammar in a way that merely supports your liking or disliking of it.
If you love grammar, don’t be the grammar police. Make sure to still prioritize vocabulary and pronunciation during the early stages. If you are grammar-averse, acknowledge the benefits of grammar study without getting too hung up on it. Make grammar an ally instead of an enemy.
Image from XKCD, by Randall Munroe. CC BY-NC 2.5
There are grammar rules that will ask you to study them rigorously and there are others that will ask you to pick them on the go. For example, virtually every English speaker (L1 and L2) knows in which order adjectives should go when producing language, but cannot pinpoint the precise rule.
For instance, you would correctly say “a red little bird” instead of “a little red bird”, even if you wouldn’t know why.
A big part of a language's grammar doesn’t have a reason, it is just what it is because people decided to speak that way without any prior written agreement. Whether it is correct or it isn’t won’t matter for your ability to communicate.
Image from XKCD, by Randall Munroe. CC BY-NC 2.5
This means that you need the double approach of learning grammar from language and learning language from grammar. You will progress faster if you start with the former and resort to the second when you need it.
Study grammar progressively as you find examples of different rules in the content you consume. Chances are that you’ll need to know how to construct the past tense soon enough, but you don’t need to know all the types of past tense a language has, conjugations, irregular verbs, etc.
Instead, take what you need and move on. You will encounter that feature again and learn a bit more about it.