Well, this team has worked out for me so far, and I'm wondering if I can get some fellow smogon users to help me improve it. I'll first go through the process of how the team was built. If you don’t care for this process, just skip ahead to the portion below.
Originally, the team was built around Accelgor. I had faced off against him a couple times in the ladder, and I thought he was an interesting pokemon. I used him as a suicide bomber, and it was a good sweep stopper.
Next I decided to look for a mega pokemon, and I ended up finding Mega Tyranitar. He had a good D-Dance Set, as well as some decent coverage, also making out as a good Special Wall.
Because I had Tyranitar's Sand Stream, I figured adding one poke to get a boost from the sand stream would be useful. I decided to add Excadrill, since he got the speed boost from sand rush, and had the capability to setup a swords dance, and already have the boosted speed from Tyranitar. He also served as a rapid spinner, so I could clear the rocks out from under Accelgor so that he would have full health for the Final Gambit.
Next came Gengar. Gengar was added as a hard hitter, and because I was in dire need of special attackers at this point. He carried the sash and D-Bond, so that he could hit hard, take a hit and then take someone down with him. Gengar was also known as a good special attacker in general, so adding him to the team seemed like a good idea.
Next addition was Infernape. Most of my team was either strong and fast, but with little coverage, or slow with some decent coverage. Infernape seemed to cover both aspects. He was fast, and had some good type coverage.
For the last slot, I was mainly looking for some special attack power, that could also have the capability to set up and sweep. I found this is Thundrus Therian. He provided decent coverage, and allowed for some hard hits. He was a good final member to the team.
After some testing, I discovered that gengar wasn't really putting in the work that I needed. His sash often got broken, as I was not able to spin them away with excadrill, and he didn't really do much other then prove as death fodder. I had to find a replacement for him, and I preferred a ghost type to use as a spin blocker as well. This is when Chandelure came in. Chandy served as a revenge killer, a spin blocker, and a sub breaker. Using infiltrator, chandelure was able to bypass substitutes, meaning it could easily kill stallers and teams that rely on screens.
After adding chandelure, I discovered that my team had a major weakness to rocks, and any smart player with a ghost on their team could see excadrill and spin block me, making it impossible to get the rocks out of the way. This meant that I would need to remove a rock weakness, and possibly add a resistance. I decided that the most removable pokemon on the team was Accelgor, the original pokemon the team was based upon. At this time, I had also found that tyranitar was working better as a special wall than an offensive mega. So, as a solution to both problems, I added mega mawile. This gave some good offensive power, along with a resistance to rocks. Now that I had mega mawile, tyranitar lost its mega stone and was given the assault vest to help with special defense.
Thats the overview of how the team was made, so here's the team as it stands:
Excadrill Air Baloon
252 Atk / 252 Spe / 4 HP
Adamant
Ability: Sand Rush
-Earthquake
-Rock Slide
-Rapid Spin
-Swords Dance
Excadrill Serves not only as a rapid spiner, but as a sweeper. Using the sandstorm set by tyranitar, he can outspeed most things, and even after the sand dies out, he is still decently fast, and with a swords dance can still do lots of damage.
Tyranitar @Assault Vest
252 SpDef / 252 Atk / 4 SpAtk
Sassy
Ability: Sand Stream
-Earthquake
-Stone Edge
-Crunch
-Fire Blast
Tyranitar's main purpose is to set up the sand for excadrill, and go down with a fight, however he can server as a really good special wall.
Chandelure @Choice Scarf
252 SpAtk / 252 Spe / 4 SpDef
Timid
Ability: Infiltrator
-Fire Blast
-Shadow Ball
-Energy Ball
-Psychic
Chandelure serves as a really good revenge killer, along with a sub breaker. Since Dual Screen/Substitute klefki is very lively in the metagame, a fire blast from this thing will easily break that.
Thundurs-Therian @Quick Claw
252 SpAtk / 252 Spe / 4 Hp
Timd
Ability: Volt Absorb
-Thunderbolt
-Focus Blast
-Nasty Plot
-Grass Knot
Thundurus just plays the role of the general special attack, who at the same time can deal good damage without setting up.
Infernape Expert Belt
252 Atk / 252 Spe / 252 SpDef
Jolly
Ability: Iron Fist
-Thunderpunch
-Fire Punch
-Mach Punch
-Close Combat
With good coverage, speed and attack, infernape is a very good addition to my team. His ability Iron Fist greatly boost three out of four moves, one of which has priority. His close combat also packs a strong punch despite only being boosted by STAB.
Mawile @Mawilite
252 Atk / 252 HP / 4 SpDef
Adamant
Ability: Intimidate
-Play Rough
-Iron Head
-Swords Dance
-Sucker Punch
Being the final member to the team, mawile is our mega. Mawile has good coverages, and is bulky enough to tank a hit. Especially a physical hit, since intimidate will drop their attack first turn, allowing it to get one swords dance up. Hits hard, however not too fast.
Originally, the team was built around Accelgor. I had faced off against him a couple times in the ladder, and I thought he was an interesting pokemon. I used him as a suicide bomber, and it was a good sweep stopper.
Next I decided to look for a mega pokemon, and I ended up finding Mega Tyranitar. He had a good D-Dance Set, as well as some decent coverage, also making out as a good Special Wall.
Because I had Tyranitar's Sand Stream, I figured adding one poke to get a boost from the sand stream would be useful. I decided to add Excadrill, since he got the speed boost from sand rush, and had the capability to setup a swords dance, and already have the boosted speed from Tyranitar. He also served as a rapid spinner, so I could clear the rocks out from under Accelgor so that he would have full health for the Final Gambit.
Next came Gengar. Gengar was added as a hard hitter, and because I was in dire need of special attackers at this point. He carried the sash and D-Bond, so that he could hit hard, take a hit and then take someone down with him. Gengar was also known as a good special attacker in general, so adding him to the team seemed like a good idea.
Next addition was Infernape. Most of my team was either strong and fast, but with little coverage, or slow with some decent coverage. Infernape seemed to cover both aspects. He was fast, and had some good type coverage.
For the last slot, I was mainly looking for some special attack power, that could also have the capability to set up and sweep. I found this is Thundrus Therian. He provided decent coverage, and allowed for some hard hits. He was a good final member to the team.
After some testing, I discovered that gengar wasn't really putting in the work that I needed. His sash often got broken, as I was not able to spin them away with excadrill, and he didn't really do much other then prove as death fodder. I had to find a replacement for him, and I preferred a ghost type to use as a spin blocker as well. This is when Chandelure came in. Chandy served as a revenge killer, a spin blocker, and a sub breaker. Using infiltrator, chandelure was able to bypass substitutes, meaning it could easily kill stallers and teams that rely on screens.
After adding chandelure, I discovered that my team had a major weakness to rocks, and any smart player with a ghost on their team could see excadrill and spin block me, making it impossible to get the rocks out of the way. This meant that I would need to remove a rock weakness, and possibly add a resistance. I decided that the most removable pokemon on the team was Accelgor, the original pokemon the team was based upon. At this time, I had also found that tyranitar was working better as a special wall than an offensive mega. So, as a solution to both problems, I added mega mawile. This gave some good offensive power, along with a resistance to rocks. Now that I had mega mawile, tyranitar lost its mega stone and was given the assault vest to help with special defense.
Thats the overview of how the team was made, so here's the team as it stands:

Excadrill Air Baloon
252 Atk / 252 Spe / 4 HP
Adamant
Ability: Sand Rush
-Earthquake
-Rock Slide
-Rapid Spin
-Swords Dance
Excadrill Serves not only as a rapid spiner, but as a sweeper. Using the sandstorm set by tyranitar, he can outspeed most things, and even after the sand dies out, he is still decently fast, and with a swords dance can still do lots of damage.

Tyranitar @Assault Vest
252 SpDef / 252 Atk / 4 SpAtk
Sassy
Ability: Sand Stream
-Earthquake
-Stone Edge
-Crunch
-Fire Blast
Tyranitar's main purpose is to set up the sand for excadrill, and go down with a fight, however he can server as a really good special wall.

Chandelure @Choice Scarf
252 SpAtk / 252 Spe / 4 SpDef
Timid
Ability: Infiltrator
-Fire Blast
-Shadow Ball
-Energy Ball
-Psychic
Chandelure serves as a really good revenge killer, along with a sub breaker. Since Dual Screen/Substitute klefki is very lively in the metagame, a fire blast from this thing will easily break that.

Thundurs-Therian @Quick Claw
252 SpAtk / 252 Spe / 4 Hp
Timd
Ability: Volt Absorb
-Thunderbolt
-Focus Blast
-Nasty Plot
-Grass Knot
Thundurus just plays the role of the general special attack, who at the same time can deal good damage without setting up.

Infernape Expert Belt
252 Atk / 252 Spe / 252 SpDef
Jolly
Ability: Iron Fist
-Thunderpunch
-Fire Punch
-Mach Punch
-Close Combat
With good coverage, speed and attack, infernape is a very good addition to my team. His ability Iron Fist greatly boost three out of four moves, one of which has priority. His close combat also packs a strong punch despite only being boosted by STAB.
Mawile @Mawilite
252 Atk / 252 HP / 4 SpDef
Adamant
Ability: Intimidate
-Play Rough
-Iron Head
-Swords Dance
-Sucker Punch
Being the final member to the team, mawile is our mega. Mawile has good coverages, and is bulky enough to tank a hit. Especially a physical hit, since intimidate will drop their attack first turn, allowing it to get one swords dance up. Hits hard, however not too fast.