Inflected Indo-European languages: which cases should you concentrate on first?

I came across a page here the other day showing frequency of case usage for Croatian, a good example of an inflected Indo-European language with seven cases (depending on how you count them). While case usage varies by language, four to seven or so is usually the norm for Indo-European languages, and this survey of case usage may help with choosing which cases to concentrate on first if you find yourself drowning in grammatical information and want to concentrate on frequently-used forms first. This is especially important with active use, since you want to build up an instinct for the forms you'll be using the most often and this will cut down on the time you spend forming what to say in your mind before you say it.

According to the study, the three most-used cases are the nominative (no surprise there), accusative, and then genitive. Put these three together and you have already covered 80%. least common is also not surprising: th evocative. Nominative frequency tends to vary quite a bit, while accusative is quite stable at 25 to 28%. Genitive is 11 to 16%, locative 5 to 8%, instrumental 4 to 6%, dative varies a bit more at 6 to 15%, vocative is just 0 to 6%.