For the Gym Leader's time I'm thinking something like this
Bunnelby: One of the many physical attackers on this team (Yeah, I accidentally infested this team with Physical attackers, but I decided to work with my limits), its got a nice amount of attack that lets it abuse certain moves like a semi powerful Return/Tackle (If Return isn't our TM), and Quick attack can put the hurt on some pokemon
Staravia: Basically creates a semi bird spam core with Fletchling, its quite fast, has access to Initmidate which can help it out quite nicely by making it a bit bulkier, and is also rather helpful for Chansey. Its got rather powerful stab, Wing Attack is quite nice early game since it gives the opponent a powerful move to use against our fighting types who can hurt Chansey
Fletchling: A nice powerful priority abuser. Like I said earlier, this pokemon can work really well with Staravia by creating a semi bird spam core. Also, like Staravia Fletchling helps the opponent out by giving them another weapon against fighting types.
Slowpoke: Ironically the only special attacker on the team. Slowpoke can help the opponent out by giving them a poke who can attack our Ghastly's with SE coverage moves, especially when considering how we don't have any Ghost type move to hit it with. It also creates a semi stall core with Chansey
Marill: Not really the best poke on the team, but it can do some damage. While it doesn't get a STAB move. it does make up for it with a powerful Tackle/Return, also it does get rock coverage but that doesn't really matter much
Chansey: The signature pokemon of the team. It is a powerful wall who can really do some work at its job. It has access to SR and it gets both a recover move and a status healing move. It can also do a moderate amount of damage with Toxic/Sesmic Toss (Preferably the former)
Also another thing, can we please not rely heavily on TM and Egg moves, we have barely any pokemon to get egg moves from atm and also we haven't even gotten a single tm yet, the closest thing being the SR tutor, I also think we shouldn't rely on Pokes we haven't encountered yet unless its a signature poke
Speaking of TMs, what is the TM the gym leader gives us after we defeat them? I'm thinking Return is our best choice