Okay, to start... this is really hard to do.
You will need:
-3DS with Pokemon Yellow, Red and Blue, and Gold, Silver and Crystal
-Ruby, Sapphire and Emerald on legit cartridges, as well as Fire Red/Leaf Green
-HeartGold and SoulSilver
-Diamond, Pearl and Platinum
As you can see, you'll need to spend a LOT of money. It isn't worth it unless you really want to do it for the lolz
To start, let's start with Platinum's dex. Obviously, you'll need more than one DS to transfer D/P's exclusives over, and use the tweaking glitch to get all the event only Pokemon.
Now, using the DS lite, you can insert R/S/E/FR/LG and transfer over their entire pokedexs.. congrats! You got 3 dexs done!
Now, this is there the 3DS comes in.
Using the virtual consols, play through GSC and use bank to transfer them to Platinum. Use Red/Blue/Yellow for the Mew glitch, and any other Pokemon you're missing. You'll likely need all three games for the starter lines, and Crystal for Celebi
As easy as I made it sound here... it isn't easy and will likely take at least a year to complete. Good luck if you choose to do this!