How to improve: 519-520-521-Pidove-Tranquill-Unfezant

1.Stats: Should Unfezant get a stat boost, Evolution, Mega Evolution or nothing?
Unfezant cannot evolve further. So there is that.

A Mega Evolution for early birds is generally rare, as so far only Pidgeot got one, as it desperately needed a major stat boost. If it gone, however, it would still be crippled by its lack of moves.

A stat boost seems also unlikely, as of now Unfezant has the second highest BST of all early bird Pokémon, coming right behind Talonflame's 499 BST. So it can only get another 10 BST boost, which would be nice, but not too helpful. However, since it already got a stat boost, another one in the near future seems unlikely.

 2.Should Unfezant get more abilities?
Almost certainly, however, Unfezant doesn't have much moves that would work well with a new ability. Most thematically fitting abilities are stuff like Own Tempo, Keen Eye, Quick Feet and Tangled Feet, neither of which are better than what it already has.

Because it has no recoil moves either, Reckless wouldn't work at all. And since it is nerfed terribly, Gale Wings is largely useless, and it has a usable Speed for lower tiers anyways. Due to wide range of Status moves it gets Prankster would be useful, and Intimidate and Defiant would just be generically useful.

 3. Should Unfezant get more moves?
Absolutely. Some moves include:

1. More Flying and Normal moves: Unfezant is the most lacking bird since Noctowl in STAB department. It doesn't even get Drill Peck. That's bad.
2. More critical-hit moves: Unfezant's ability Super Luck only works for three moves, Sky Attack, Night Slash and Air Cutter, everything else is useless without Scope Lens.
3. Anything, really. Swords Dance, Nasty Plot, Reversal, heck evel Flail would be good on it.

 4.What additional typing Unfezant can have?

Most obvious types for Unfezant are Psychic, due to moves like Lucky Chant, Hypnosis, and Psych Up and Dark, due to Taunt and Night Slash. Everything else just doesn't work, really.