" ????? received the Shiny Charm ! "

• Capture all the Pokémons in Kalos. Run in every routes, surf every waters, search the skies and hunt in the Safaris of your friends! to get every last of them. This maybe a long step but it's crucial to get some other Pokémons later! Evolve, train them and breed them to fill your pokédex!
• Breed a rare pokémon. (Preferably not from Kalos!) I used Slakoth. Feebas, Buizel, Bonsly are also very prized. Breed a lot of them. Maybe 3-4 boxes or more! It maybe long and tedious, but hey! What about doing some Masuda Method at the same time? You might get a shiny! (It was my case after less than 60 eggs) These little treats will do nicely to get almost every basic stage pokémon!
• Ask for fair trades. How many people you see asking for shiny Pokémon and they don't give out one? Or people asking for legendary pokémon for a basic pokémon? Don't be one of those! If you want a legendary pokémon, trade/deposit one! If you ask fair trades, you'll have no problem at all to get every Pokémons you need! Pokémons evolving by trading with a item are rare. Pokémons evolving with happiness are also rare and hard to come by. But if you ask again for a fair trade, everything is possible! Take one of your pokémon that evolve with happiness and ask for an other pokémon with the same evolution method. When you get the pokémon you wanted, deposit it and ask for an other pokémon with the same evolution method and repeat the process until you have all the pokémons you needed! I'd definitely recommend to use the Pokébank to get at least your first legendaries and trade them!
• Don't lose hope! I know sometimes the GTS feels like a empty space and sometimes all the trades will be near impossible to do. Don't stop looking! If you need a pokémon, I recommend you deposit a pokémon for it, it'll be easier to get it. Check the GTS at different hours! I was successful (Being able to trade/more fair trades on the GTS) most in the morning between 8AM to 11AM and least successful late in the evening. (7PM to 11PM) How about shouting for help? Strangers have helped me so much! Or try the Wonder Trade! How about using some pokémons nicknames for indications when trading? Nickname some of your pokémons: "Thank you!", "Got legends?", "No, sorry." and it'll help you out to negotiate and get understood! 
• Remember you don't need any of the events-only legendaries to complete your pokédex! (You don't need: Mew, Deoxys, Jirachi, Darkrai, Shaymin, Phione, Manaphy, Victini, Genesect, Keldeo, Meloetta) You can get an Celebi by using the Pokébank twice! You need a min. total of 705 pokémons caught to get the Shiny Charm!