Been playing 3 months


I did primarily Tactics for 8 months and my Rapid and Daily got to around 1500. I recommend chesstempo.com, it has unlimited Tactics puzzles, graphs and statistics.

Play longer time limits. Every game, identify a mistake you made. Try not to repeat it.
Focus more on opening principles and tactics for now, but do learn your elementary mates if you haven't yet.
Don't try to memorize long opening lines for now. It will be a waste of effort because:
1) Your opponent is unlikely to follow them beyond 4 or 5 moves.
2) You won't know what to do with the position anyway.

What we see coming and going and at the same time we know where we or them are.
We are on a big ball of water there a big fire balll there a big planet that can crush into earth good enought for me.
https://www.chess.com/article/view/study-plan-directory
"... In order to maximize the benefits of [theory and practice], these two should be approached in a balanced manner. ... Play as many slow games (60 5 or preferably slower) as possible, ... The other side of improvement is theory. ... This can be reading books, taking lessons, watching videos, doing problems on software, etc. ..." - NM Dan Heisman (2002)
https://web.archive.org/web/20140627084053/http://www.chesscafe.com/text/heisman19.pdf
"... If it’s instruction, you look for an author that addresses players at your level (buying something that’s too advanced won’t help you at all). This means that a classic book that is revered by many people might not be useful for you. ..." - IM Jeremy Silman (2015)
https://www.chess.com/article/view/the-best-chess-books-ever
Here are some reading possibilities that I often mention:
Simple Attacking Plans by Fred Wilson (2012)
https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf
http://dev.jeremysilman.com/shop/pc/Simple-Attacking-Plans-77p3731.htm
Logical Chess: Move by Move by Irving Chernev (1957)
https://web.archive.org/web/20140708104437/http://www.chesscafe.com/text/logichess.pdf
The Most Instructive Games of Chess Ever Played by Irving Chernev (1965)
https://chessbookreviews.wordpress.com/tag/most-instructive-games-of-chess-ever-played/
Winning Chess by Irving Chernev and Fred Reinfeld (1948)
https://web.archive.org/web/20140708093415/http://www.chesscafe.com/text/review919.pdf
Back to Basics: Tactics by Dan Heisman (2007)
https://web.archive.org/web/20140708233537/http://www.chesscafe.com/text/review585.pdf
https://www.chess.com/article/view/book-review-back-to-basics-tactics
Discovering Chess Openings by GM John Emms (2006)
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf
Openings for Amateurs by Pete Tamburro (2014)
http://kenilworthian.blogspot.com/2014/05/review-of-pete-tamburros-openings-for.html
https://chessbookreviews.wordpress.com/tag/openings-for-amateurs/
https://www.mongoosepress.com/catalog/excerpts/openings_amateurs.pdf
Chess Endgames for Kids by Karsten Müller (2015)
https://chessbookreviews.wordpress.com/tag/chess-endgames-for-kids/
http://www.gambitbooks.com/pdfs/Chess_Endgames_for_Kids.pdf
A Guide to Chess Improvement by Dan Heisman (2010)
https://web.archive.org/web/20140708105628/http://www.chesscafe.com/text/review781.pdf
Studying Chess Made Easy by Andrew Soltis (2009)
https://web.archive.org/web/20140708090448/http://www.chesscafe.com/text/review750.pdf
Seirawan stuff:
http://seagaard.dk/review/eng/bo_beginner/ev_winning_chess.asp?KATID=BO&ID=BO-Beginner
http://www.nystar.com/tamarkin/review1.htm
https://web.archive.org/web/20140627132508/http://www.chesscafe.com/text/hansen173.pdf
https://www.chess.com/article/view/book-review-winning-chess-endings
https://web.archive.org/web/20140708092617/http://www.chesscafe.com/text/review560.pdf
Do tactics.
Follow opening principles when you play. Namely, don't move the same piece every move. Move a new piece every turn (unless you need to deal with some threat immediately), always castle. Only once you have moved/developed all your pieces look to attack. Play towards the middle of the board instead of playing to the side.
This should get you into 1000s easily.
learn tactics by themes. acquire tactical pattern recognition. get world's champion guide to chess by polgar. it contains puzzles arrange by themes. this book will improve your tactical pattern recognition. it also contains general guide for starting up player.
https://www.amazon.com/World-Champions-Guide-Chess-Step/dp/1941270328

Study the game...learn the fundamentals...
Good Chess Books for Beginners and Beyond...
https://www.chess.com/blog/RussBell/good-chess-books-for-beginners-and-beyond
Maximize The Usefulness of Your Moves....some useful tips...
http://www.mark-weeks.com/aboutcom/aa06b18.htm