Allows for the user to easily enter and leave giveaways from the homepage of SteamGifts.

SteamGiftsEasyEnter.user.js

// ==UserScript==
// @name         SteamGifts Easy-Enter
// @homepage     https://gist.github.com/TheOdd/f2169d1ebec2b34a9c664f0928082593/
// @version      1.5.1
// @description  Allows for the user to easily enter and leave giveaways from the homepage of SteamGifts.
// @author       TheOdd
// @match        https://www.steamgifts.com/
// @match        https://www.steamgifts.com/giveaways/search?page=*
// @grant        none
// @require      http://code.jquery.com/jquery-latest.min.js
// @updateURL    https://gist.githubusercontent.com/raw/f2169d1ebec2b34a9c664f0928082593/SteamGiftsEasyEnter.user.js
// ==/UserScript==

(function() {
    'use strict';

    const xsrf_token = $("[name='xsrf_token']").attr('value')

    const giveawayCodeRegEx = /^\/(?:giveaway)\/(.+)\//

    $('a.giveaway_image_thumbnail, a.giveaway_image_thumbnail_missing').each(function() {
        const code = $(this).attr('href').match(giveawayCodeRegEx)[1]
        $(this).attr('code', code)
        $(this).removeAttr('href')
        $(this).click(function() {
            const pointsLeft = parseInt($('span.nav__points').text())
            const pointText = $(this).parent().children().first().children().first().children('span:last').text()
            const cost = parseInt(pointText.substring(1, pointText.length - 2))
            const isFaded = $(this).parent().hasClass('is-faded')
            if (pointsLeft >= cost || isFaded) {
                $.ajax('https://www.steamgifts.com/ajax.php', {
                    method: 'POST',
                    data: {
                        code: $(this).attr('code'),
                        do: isFaded ? 'entry_delete' : 'entry_insert',
                        xsrf_token: xsrf_token
                    }
                })
                $('span.nav__points').text((pointsLeft + (isFaded ? cost : -cost)).toString())
                $(this).parent().toggleClass('is-faded')
            }
        })
    })
})();

Prerequisites

Any kind of user script browser extension. I use Tampermonkey.

Links:
Tampermonkey for Chrome
Tampermonkey for FireFox

Installation

Just click the Raw button at the top right of the file to directly view the file. This will open your script extension's installation page for the script.

Usage

Click on the giveaway thumbnails on the homepage of SteamGifts to toggle entering the giveaway (e.g. leaving the giveaway if you were entered and joining if you weren't and have enough points)
The script also updates your points at the top of the page and grays out giveaways after entering them.
It also won't let you enter giveaways that you don't have enough points for.

Demo