Ninja FV

Heads up: magnemite isn't available until around 11th Gym, and both ralts and shellder come 2 Gyms later. They're still very useful to have once you get them, but you're definitely gonna have to use other pokes until you get there.

As for Flying Types, fletchling, fearow (already evolved!), and drifloon are available prior to the 3rd Gym, while murkrow spawns a little after it. If that's too late for your taste, then swoobat and vivillon are bot obtainable before the first Gym and provide a tricky path to power, while the pidove line (attained before the 2nd Gym) gives a more straightforward path (and is required for a sidequest in the midgame anyway). You've got a few options you can work with here!