Here's a thread that should drain away a good chunk of your life. So, you have 649 existing Pokemon to choose from. Mix and match them to make your own dream Pokedex. To prevent people from just taking all 649 Pokemon, lets limit it to 150, okay?
Remember, a good Pokedex should always start with Starter Pokemon (in Grass/Fire/Water order), have at least one legendary trio, at least one pseudo legendary family, 1-2 powerful legendary Pokemon with ~680 BST and end with an event exclusive legendary.
Away you go!!!
(I have a test to finish but once I do, I'll edit the OP with my own Pokedex)