What was the best chess purchase that you ever made?

I am a player with an otb rating of around 1400-1450, and I'm looking for some books/videos to help me improve. If you have any suggestion please tell me!

I think lessons

Board and pieces. Contributed more to my chess improvement than everything else combined.

The best $100 I spend all year is on diamond membership right here.  ChessMentor is a much easier way to study than books.  My visualization skills aren't the greatest and setting up a board (or boards for the variations) is kind of a pain.  I know there are youtube videos but I believe the ones here are generally higher quality and I'd probably spend the $100 just to watch IM Danny Rensch's Live Session videos.

All that said, of course I buy books too.  Paul van der Sterren's Fundamental Chess Openings is the most often used volume in my library.  Highly recommended.  You could check out danheisman.com for the coach's recommendations; he has a number of recommended books by category and rating.  You could even type something like "recommended books" in that little "search forums" box in the upper right and see what folks have recommended in the past.  Good luck.

Ok, thank you for the advice! I will look into the memberships and those other things.

Yeah, probably membership here is the best purchase I've made.

I agree with baddogno (mostly). BUT you gotta  have the time AND ambition to make use of all the premium goodies here such as unlimited access to the videos, chess mentor and tactics trainer. And you already have access to lots and lots of good articles on every phase of the game!

Ok, so which one of the benefits of the premium membership would be the best? If it is one that I could get at a lower membership level, that would of course be great, but I don't mind.

a $1000 chess set including: pieces, a board, case, clock, score book and a pen with a night for an earasor. 

What brand of those merchandise is the best?

Bad news is the ChessMentor and videos are only available at diamond level.  Good news is you could try it for a month and see if it's for you.  Actually I think the site will refund the remainder of your subscription if you're ever dissatisfied, but a month's membership kind of makes sense if you're just trying it out.  Of course as NimzoRoy has pointed out, you do have to actually do the work no matter what path you choose to improve.  Good luck.

How about following Capablanca's advice and starting with some endgames? A little book like de la Villa's "100 Endgames You Must Know" goes a long way and is a lot of fun.

I love my club kit - bag, clock, pen, scoresheets and triple weighted pieces.

Alekhine's Best Games of Chess.

The triad: 300 Chess Games by Tarrasch, 100 Selected Games by Botvinnik, and Alekhine's Best Games by you guessed it. If I wasn't working 60+ hours a week I'd be re-reading these, but for now a few Tactics on here and some G:15-10's will have to do to keep me from getting rusty.

Winning Chess Traps by Robert M. Snyder is supposed to be good but I haven't read it but I have read other of his books and there are really good.

They are around $18.

They aren't the best chess purchase but the best for me, and I haven't really gotten anything except a board, pieces, and some books.

The Seven Deadly Chess Sins by Jonathan Rowson

Everyone loses chess games occasionally, but all too often we lose a game due to moves that, deep down, we knew were flawed. Why do we commit these chess-board sins? Are they the result of general misconceptions about chess and how it should be played better? In this thought-provoking and entertaining book, Jonathan Rowson investigates, in his inimitable style, the main reasons why chess-players sometimes go horribly astray. He focuses on several underlying psychological pitfalls: Thinking (unneceessary or erroneous); Blinking (missing opportunities; lack of resolution); Wanting (too much concern with the result of the game); Materialism (lack of attention to non-material factors); Egoism (insufficient awareness of the opponent and his ideas); Perfectionism (running short of time; trying too hard); and Looseness ("losing the plot"; drifting; poor concentration). A great book for readers interested in understanding why they sometimes make the mistakes that frustrate their efforts at winning!

Ok, so I think it would be good to go over plenty of annotated games and endgames, and possibly try the memberships. Are there any books like Chernev's "Logical Chess Move by Move" that are good?

In addition to my previous comment, this other book by Rowson might be more helpful: Chess for Zebras: Thinking Differently about Black and White.

Jonathan Rowson, author of the highly acclaimed Seven Deadly Chess Sins, investigates three questions important to all chess-players: 1) Why is it so difficult, especially for adult players, to improve? 2) What kinds of mental attitudes are needed to find good moves in different phases of the game? 3) Is White's alleged first-move advantage a myth, and does it make a difference whether you are playing Black or White? In a strikingly original work, Rowson makes use of his academic background in philosophy and psychology to answer these questions in an entertaining and instructive way. This book assists all players in their efforts to improve, and provides fresh insights into the opening and early middlegame. Rowson presents many new ideas on how Black should best combat White's early initiative, and make use of the extra information that he gains as a result of moving second. For instance, he shows that in some cases a situation he calls 'Zugzwang Lite' can arise, where White finds himself lacking any constructive moves. He also takes a close look at the theories of two players who, in differing styles, have specialized in championing Black's cause: Mihai Suba and Andras Adorjan. Readers are also equipped with a 'mental toolkit' that will enable them to handle many typical over-the-board situations with greater success, and avoid a variety of psychological pitfalls. Chess for Zebras offers fresh insights into human idiosyncrasies in all phases of the game. The depth and breadth of this book will therefore help players to appreciate chess at a more profound level, and make steps towards sustained and significant improvement.