Alright so, I'll start by going over every Pokemon one by one.
Mismagius is a Pokemon with a great special attack and a great speed. 105 base stat each to be exact. So I would really emphasize using hard hitting Special attack moves. I find that when you have a Pokemon that has a high special attack or attack along with a high speed you can get by, by hitting hard and fast. Ultimately knocking out your opponent without worry about your opponent hitting you. This doesn't always work, but I think it's a great strategy for an in game team. So far the best move you have for Mismagius is Shadow Ball. It's really going to utilize Mismagius's special attack and get double the power since you're pairing up a ghost type move with a ghost type Pokemon. I'm not a big status move person and I find that it's really easy to get by without status moves in your in game team. So I would suggest taking out Pain Split and Perish song and replacing them with either Thunderbolt, Psychic, Hyper Beam, Energy Ball, or Dark Pulse. All are high power special attack moves that Mismagius can use to its advantage. I would also suggest removing thief since it's a physical low powered move and you won't be able to take advantage of stealing moves if your Mismagius is already holding an item.
Now I would personally dispose of Furret and replace it with a better Pokemon, but since this is in game I think you can get away with it. Furret's best offensive stat is its attack of 76. So my thoughts are to completely toss out any special moves you plan to equip with Furret since its special attack is only 45. Also Furret doesn't have much of a defense or a special defense to protect itself with so you really want to utilize its attack power. Shadow Claw is a great physical move for Furret, but my only concern is that you already have three ghost Pokemon on your team who are better suited for using ghost moves. So in this case I would say try to make your moves more diverse when it comes to Furret. You're already testing the waters with a mostly one type team so you need Furret and Dragonair to make up for any of your ghost Pokemon weaknesses. Some good physical moves Furret can learn are Iron Tail, Brick Break, Giga Impact, Strength, and U-Turn. I would really consider U-Turn since it has a high attack that Furret can use and it will also switch out Furret if it were to encounter a dangerous foe.
I'd say Gengar is the Pokemon on your team that can use the strategy of a high special attack and speed combo the best. The most important move that you can give Gengar and the one that you already have is in my opinion Shadow Ball. Gengar can use this move better then any other Pokemon on your team since its high special attack and ghost typing will be a great match up with the already powerful special ghost type move. Dark Pulse is also a great move for Gengar, but I just want to say that if you teach Gengar Dark Pulse then you might not want to also teach it to Mismagius since it's important to vary up your moves. Also keep in mind that Gengar is a dual type. I always try to use both types as well as I can and this situation is no exception. Sludge Bomb is what I feel is the best poison move you can teach it. It has a high special attack and will strike harder with Gengar's dual typing. Lastly I would take out Night Shade and replace that with either Focus Blast, Hyper Beam, Thunderbolt, Energy Ball or Psychic.
Okay so Drifblim's attack and special attack are fairly even with attack being an 80 base stat and special attack 90. So in this case I would incorporate both physical and special moves. For the most part I think you can leave Fly and Shadow ball alone. For the other two moves you could possibly add some variety by replacing them with Silver Wind, Thunderbolt, Psychic, Return, Hyper Beam, and possibly Explosion, but I'm always iffy on recoil moves like Explosion so that's your call.
Last, but not least you have Dragonair which is the most important Pokemon on your team. Dragonair will have to make up for any shortcomings your ghost pokemon have along with Furrets not so great stats. Most importantly Dragonair is going to need a Dragon type move which you have Dragon Rush as of now so that's fine. I do suggest once you evolve it into Dragonite or level Dragonair up to level 61 you should teach it Outrage. If you already have one water move for Dragonair then I wouldn't bother teaching it another. In this case I don't think it matters if you choose Surf over Aqua Tail or the other way around. I mean once Dragonair evolves it will have a much higher attack that will go hand in hand with Aqua Tail, but I think Surf is a high powered enough special move to also work with Dragonair/Dragonite. So my suggested moves for an evolved Dragonair would be Earthquake, Outrage, Surf/Aqua Tail, and Giga Impact.
Overall make sure Dragonair and Furret have the attacks to back up your three ghost types. Also really try to vary your ghost Pokemon moves. I know it's hard because they generally learn the same set whether it be from level up or TMs, but I'm sure once you divide it out each ghost type should have fairly different sets of moves.
