Playing on Omega Ruby and here is my team so far.

Gengar
Tentacruel
Flareon
Skarmory

As you can see, I prefer first and 2nd gen pokemons.

Any idea for last 2 spots? Im new to the competitive.

Scizor
Alakazam

Gengar is all you need... Shadow ball will-o-wisp shockwave and thief

Just based on your team, I see you need a lot of practice

I would recommend going on pokemonshowdown.com and doing some battles or watch replays of people on too of the ladder and see what works for them