Of course, at some point, you'll need both. That said, especially if you will be dealing with more written than spoken English, learn grammar first. It is usually simpler and quicker to look up a word than it is to look up a grammatical structure.

hello, Both. If you learn lots of vocabulary without being able to build correct sentences,they might not make sense to the listener ,so in order to build comprehensible sentences grammar and its rules are essential. If you just learn grammar rules and don't care to increase your vocabulary you won't be able to say and express yourself well .Your ability of speaking would be limited .So both integrate to make you speak good comprehensible English !