(Edit: Fixed image Error) (Sorry about some of the cut-off images, I won't use Showdown Teambuilder for my images next time.)
I'm unsure if this team is really bad or not as I'm very new to the competitive scene. If I should just scrap the whole team or a good portion than I will, as I'm very unsure of what's good and what's not good. I would also really appreciate any recommendations for Pokemon that I can swap out, as I know that you'll probably spot some large flaw in my team other than fairy coverage. I've been playing it on Showdown and it's been doing OK. I usually lose due to my lack of knowledge of how to counter things rather than problems with my team.

Forretress
Item: Leftovers
Ability: Sturdy
EV Spread: 252 HP, 252 Defense, 4 Sp. Def
Nature: Relaxed (+Def,-Spe)
Moves:
-Rapid Spin
-Stealth Rock
-Toxic Spikes
-Explosion
It's a pretty standard setup for Forretress. I like Forretress as a hazard setter over Ferrothorn just because I feel that he is better at getting up hazards and rapid spinning in the first few turns, and then just getting out. I like Toxic Spikes over spikes because the rocks do enough damage to the things that I need to, and the toxic spikes help with bulky pokemon that are difficult to take out. I choose explosion over U-Turn because I can often explode into a Mega Charizard setting up, and then take it out with my

Trevenant
Item: Leftovers
Ability: Natural Cure
EV Spread: 252 HP, 252 Sp. Def, 4 Attack
Nature: Careful (+SpD,-SpA)
Moves:
-Wood Hammer
-Shadow Claw
-Will-O-Wisp
-Rest
This setup for Trevenant makes him into an absolute tank. He can take a lot of super effective attacks, along with being a good switch-in for attacks that would otherwise KO one of my Pokemon. Wood Hammer, Shadow Claw, and Will-O-Wisp are fairly self explanatory, and he usually gets what I need him to do done. I can use rest and then switch out, and Natural Cure cures sleep allowing him to be continuously useful.
Mega Gardevoir
Item: Gardevoirite
Ability: Synchronize
EV Spread: 172 HP, 252 Sp. Atk, 84 Speed
Nature: Modest (+SpA, -Atk)
Moves:
-Calm mind
-Dazzling Gleam
-Shadow Ball
-Thunderbolt
Mega Gardevoir is an incredibly strong special attacker that I use as my main fairy type Pokemon and I also use it for a lot of type coverage. The moveset is pretty standard, Shadow Ball is for Psychic/Shadow type coverage (Not Aegislash because of Shadow Sneak), and thunderbolt is really good for getting water types that don't expect a lightning move on Gardevoir.
Salemance
Item: Focus Sash
Ability: Moxie
EV Spread: 252 Attack, 252 Speed, 4 Sp. Def
Nature: Jolly (+Spe, -SpA)
Moves:
-Dragon Dance
-Dragon Claw
-Earthquake
-Aerial Ace
Salemance is a fantastic sweeper for my team. I once swept somebody's whole team with him: http://replay.pokemonshowdown.com/ou-108893640. He is an excellent counter for almost all dragon type pokemon, and has prevented my whole team from dying to things like Mega Garchomp and/or Charizard X. His main objective is to be sent in after a Pokemon faints, Dragon Dance, take whatever hits him thanks to Focus Band, and then take out almost any Pokemon with his moves' type coverage. He is also very fast, and outspeeds almost anything that he needs to outspeed, coupled with incredibly deadly attack. I enjoy this setup a lot, the downside being priority moves (For which I have to switch out) and the fact that he's frail and doesn't deal well with stealth rocks.
Talonflame
Item: Leftovers
Ability: Flame Body (Just kidding, Gale Wings)
EV Spread: 252 Attack, 248 Speed, 8 HP
Nature: Adamant (+Atk, -SpA)
Moves:
-Flare Blitz
-PRIORITY BRAVE BIRD
-U-Turn
-Steel Wing
You can more or less understand the objective of Talonflame, and he's proved invaluable to my team in terms of type coverage and taking out weakened Pokemon with a neutral PRIORITY BRAVE BIRD. The U-turn does a lot of damage against psychic type Pokemon, and and allows him to switch into his opposite, Rotom Wash. I swapped Steel Wing for Roost because I didn't often get a chance to use Roost seeing as how frail he is, and I use leftovers to lessen the recoil on his attacks already.
Rotom-Wash
Item: Leftovers
Ability: Levitate
EV Spread: 232 HP, 56 Sp. Atk, 220 Spe
Nature: Modest (+SpA, -Atk)
Moves:
-Volt Switch
-Hydro Pump
-Will-O-Wisp
-HP Ice
Another pretty standard way to run Rotom-Wash. His excellent typing allows me to counter other Rotom-Washes along with being a good switch in for most attacks. I must admit however that I don't use Will-O-Wisp very much, and HP Ice can often be super effective, but never does much damage at all. I think that it's my lack of experience, but otherwise Rotom-Wash has been an excellent part of my team no matter how I use him.
Again, I really appreciate negative feedback, as long as you recommend something that I can do to fix it, or something I can change. Even "This team sucks, start again", although I do want to incorporate some of these pokemon in whatever my new team will be because I like them.
I'm unsure if this team is really bad or not as I'm very new to the competitive scene. If I should just scrap the whole team or a good portion than I will, as I'm very unsure of what's good and what's not good. I would also really appreciate any recommendations for Pokemon that I can swap out, as I know that you'll probably spot some large flaw in my team other than fairy coverage. I've been playing it on Showdown and it's been doing OK. I usually lose due to my lack of knowledge of how to counter things rather than problems with my team.

Forretress
Item: Leftovers
Ability: Sturdy
EV Spread: 252 HP, 252 Defense, 4 Sp. Def
Nature: Relaxed (+Def,-Spe)
Moves:
-Rapid Spin
-Stealth Rock
-Toxic Spikes
-Explosion
It's a pretty standard setup for Forretress. I like Forretress as a hazard setter over Ferrothorn just because I feel that he is better at getting up hazards and rapid spinning in the first few turns, and then just getting out. I like Toxic Spikes over spikes because the rocks do enough damage to the things that I need to, and the toxic spikes help with bulky pokemon that are difficult to take out. I choose explosion over U-Turn because I can often explode into a Mega Charizard setting up, and then take it out with my

Trevenant
Item: Leftovers
Ability: Natural Cure
EV Spread: 252 HP, 252 Sp. Def, 4 Attack
Nature: Careful (+SpD,-SpA)
Moves:
-Wood Hammer
-Shadow Claw
-Will-O-Wisp
-Rest
This setup for Trevenant makes him into an absolute tank. He can take a lot of super effective attacks, along with being a good switch-in for attacks that would otherwise KO one of my Pokemon. Wood Hammer, Shadow Claw, and Will-O-Wisp are fairly self explanatory, and he usually gets what I need him to do done. I can use rest and then switch out, and Natural Cure cures sleep allowing him to be continuously useful.
Mega Gardevoir
Item: Gardevoirite
Ability: Synchronize
EV Spread: 172 HP, 252 Sp. Atk, 84 Speed
Nature: Modest (+SpA, -Atk)
Moves:
-Calm mind
-Dazzling Gleam
-Shadow Ball
-Thunderbolt
Mega Gardevoir is an incredibly strong special attacker that I use as my main fairy type Pokemon and I also use it for a lot of type coverage. The moveset is pretty standard, Shadow Ball is for Psychic/Shadow type coverage (Not Aegislash because of Shadow Sneak), and thunderbolt is really good for getting water types that don't expect a lightning move on Gardevoir.
Salemance
Item: Focus Sash
Ability: Moxie
EV Spread: 252 Attack, 252 Speed, 4 Sp. Def
Nature: Jolly (+Spe, -SpA)
Moves:
-Dragon Dance
-Dragon Claw
-Earthquake
-Aerial Ace
Salemance is a fantastic sweeper for my team. I once swept somebody's whole team with him: http://replay.pokemonshowdown.com/ou-108893640. He is an excellent counter for almost all dragon type pokemon, and has prevented my whole team from dying to things like Mega Garchomp and/or Charizard X. His main objective is to be sent in after a Pokemon faints, Dragon Dance, take whatever hits him thanks to Focus Band, and then take out almost any Pokemon with his moves' type coverage. He is also very fast, and outspeeds almost anything that he needs to outspeed, coupled with incredibly deadly attack. I enjoy this setup a lot, the downside being priority moves (For which I have to switch out) and the fact that he's frail and doesn't deal well with stealth rocks.
Talonflame
Item: Leftovers
Ability: Flame Body (Just kidding, Gale Wings)
EV Spread: 252 Attack, 248 Speed, 8 HP
Nature: Adamant (+Atk, -SpA)
Moves:
-Flare Blitz
-PRIORITY BRAVE BIRD
-U-Turn
-Steel Wing
You can more or less understand the objective of Talonflame, and he's proved invaluable to my team in terms of type coverage and taking out weakened Pokemon with a neutral PRIORITY BRAVE BIRD. The U-turn does a lot of damage against psychic type Pokemon, and and allows him to switch into his opposite, Rotom Wash. I swapped Steel Wing for Roost because I didn't often get a chance to use Roost seeing as how frail he is, and I use leftovers to lessen the recoil on his attacks already.
Rotom-Wash
Item: Leftovers
Ability: Levitate
EV Spread: 232 HP, 56 Sp. Atk, 220 Spe
Nature: Modest (+SpA, -Atk)
Moves:
-Volt Switch
-Hydro Pump
-Will-O-Wisp
-HP Ice
Another pretty standard way to run Rotom-Wash. His excellent typing allows me to counter other Rotom-Washes along with being a good switch in for most attacks. I must admit however that I don't use Will-O-Wisp very much, and HP Ice can often be super effective, but never does much damage at all. I think that it's my lack of experience, but otherwise Rotom-Wash has been an excellent part of my team no matter how I use him.
Again, I really appreciate negative feedback, as long as you recommend something that I can do to fix it, or something I can change. Even "This team sucks, start again", although I do want to incorporate some of these pokemon in whatever my new team will be because I like them.