Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
I think another potentially good partner for Nagandel would be Keldeo. Chansey, AVTar, and Heatran as well as Weavile and Scarf Greninja don't appreciate Keldeo coming in and threatening immediately. Yes it is susceptible to spikes but imo with all the new defoggers (and old ones) you could...
IMO I think Zeraora will function really well as a cleaner as well. It already will force out the likes of CeleFerroPex and will easily be able to get off a Work Up and clean from their. I think people are underselling it because yes while its offensive stats aren't world beating it has a decent...