Studying Endgame or opening


Start with endgames ASAP, no matter your rating. Get at least the most basic endgames down. Get a general idea how to play endgames, too.
About openings, before rating 1000 basically with white open with one of the moves 1. e4, 1. d4, 1. Nf3 or 1. c4, and then follow general opening principles. Especially develop your pieces. You have much better chances to archieve anything if you have many pieces on active squares.
Around rating 1000, you may want to start learning some main lines and have general ideas about the openings of your choice, with a special focus on opening traps.