What you'll need:
>http://pastebin.com/73K1Xa3p
Checklist:
>http://imgur.com/a/EiW72
List of eligible Pokemon to obtain every ribbon available:
>http://pastebin.com/jueupZAX

>Complete Guides
Gen III-VI ribbons:
>https://i.imgur.com/HEnFtGR.jpg
Gen VI ribbons only:
>http://i.imgur.com/8zY9Bbf.png

>Guides to Contests
Psypoke's Gen III Contest Guide/Overview:
>http://www.psypokes.com/rs/contest.php
Pokeblock Recipe Guide:
>https://www.reddit.com/r/pokemonribbons/comments/11su8j/pok%C3%A9block_recipes_to_give_a_pok%C3%A9mon_perfect/?st=iys9akss&sh=db9c6a28
Bulbapedia’s Contest Move Combinations List:
>http://bulbapedia.bulbagarden.net/wiki/Contest_combination
Super Contest Guide & Strategies:
>http://www.serebiiforums.com/showthread.php?230854-Pokemon-Super-Contest-Strategies

>Guides to the Battle Facilities
AltWFC Guide (to get the World Ability Ribbon):
>https://github.com/polaris-/dwc_network_server_emulator/wiki#nintendo-dsdsi3ds2ds-configuration
Smogon's Guides:
Battle Tower for Gen IV:
>http://www.smogon.com/ingame/bt/dp_bt_intro
Battle Maison Super Triples:
>http://www.smogon.com/forums/threads/battle-maison-discussion-records.3492706/page-32#post-5049375
Battle Tree Super Doubles:
>http://www.smogon.com/forums/threads/battle-tree-discussion-and-records.3587215/page-55#post-7207168

FAQ:
>My favorite Pokemon isn’t eligible for every ribbon, what now?
The general advice is to collect whatever ribbons that Pokemon can legally obtain. Use a Pokemon that has meaning to you and have fun collecting.
>Why won’t the game let my Pokemon enter the Lv. 50 Gen III Battle?
Gen III doesn’t scale levels down, so as soon as they reach Lv. 51, they can no longer get the Lv. 50 Battle Tower ribbon. This reason is why Shadow Dragonite and Shadow Tyranitar can't get every ribbon, because you catch them at Lv. 55.
>Why did my gold Contest Memory Ribbon become blue in Gen VII?
No idea, blame GameFreak

Last one got archived.