Everybody has his/her own terms of learning curve. Me for example, I've learned PHP (webcoding) by watching a simple (I mean it really like that) HTML and CSS coding, how they designed a simple website in Photoshop, sliced it in different necessary parts, and made their simple plain CSS and usual header, body and foot pattern. Afterwards searching and finding websites like w3schools.com made it absolutely precious for me and my website coding.
Examples:
Intro
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Intro of my page with an animated clouds background. Fast to load, approx 4 MB sized clip. Without music.
Design Page
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Design website, main page. Animated gifs down below, interactive music (playes if tab focused), anchor scrolling, and more.
Gallery
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A simple gallery viewer. Made one firstly for my Silkroad PServer, showing the newest changes, players battling Medusa and Roc, etc. Made this one afterwards, while getting into YouTube Partnership, because of Warframe and Blade & Soul.
"WIP, not sure what to do with it yet"-Site :D
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My hardest work on so far. 90% javascript. Interactive background globe (traces mouse behavior, if cycling and playing around with the tiles). Animated sidepanel. Interactive music as well. Every page being fully jQuery based, which allows page and <div> alteration without reloading/refreshing websites. Also quotes of the history, changing in few seconds dependently on the length of the string: The longer it is, the more time to read.
PHP in terms of SQL, I simply took some PHP scripts here, most of them where pre-done, and read them, comprehend them afterwards like "what does actually what" and tried to script my own, altered them, changed values. I don't remember the name anymore. AFAIK it was a woman coding some usual "change character stats and teleport afterwards"-scrolls, "making full GM"-scroll things, which involved the usual "if item X used, do in stored-procedure-1337 the following process XYZ".
Making it more valuable, browsing on websites, which are explaining the necessity of using specific PHP clusters, parameters, or at least to start with "How to create a proper Stored Procedure fetching from programs" made it pretty easy doing your own thing without cheating anywhere. And since you have given incoming packets from your module, which you want to declare, order, alter/renew, and execute to your database, you want to learn that part of PHP pretty heavily on your own or with some guides.
You might able to get your stuff together and create a whole new skilltree experience. For example, my unique skilltree "Impure" is based upon poison and zombification. To unlock the tree, you have to do few quests. It is not an item which unlocks it. Checking that value "if character has been rewarded 3 specific quests, give skillmastery 123 to player XYZ" - teleporting will reveal the new mastery. Every new skillrow has to be unlocked with either quest items or with X-amount of killed special mobs (same process here about teleporting to refresh. It is a usual "bypass" thing, since we cannot obtain the opcode of this one here to "live-refresh" our meanings).
Example:
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Quite an old screenshot, but overall thats what it includes.
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Just a small proof, since people kept flagging and insulting me that I am not the owner of that skill mastery.
Proxy stuff isn't learned that easily. You have to know some basic programming first, no matter in C++ or C# (people used to use C# for everything, but keep in mind, it is easily to decompile, if not secured the backend). Nothing to tell here more than: Git gut in it first :P
Packets, learning about packets is firstly learning what ASM is. ASM is used for altering your client, gameserver module, shardserver module, etc. like for increasing your character level cap, skilltree level cap, total skilltree level cap, (oddly) quest level cap, job level cap, etc. You will get the clue, if you have some experience in it.
About the other stuff, you might check the forums here. There are some easy guides for it.