Atlas elite can be a huge help if you can afford it. Mostly for better troop training abilities. The shard bonus is unlikely to be a large source of shards unless your team has a good amount of land and high level infrastructure.
Many people save some troops to revive in between training events. Reviving gives more points for your time, hats, and gold than training new troops. Just make sure not to get too close to the cap on your revive pool in case you need to defend your team
For prim leveling event, remember that leveling Atlas riders also counts. Use diamonds for gold if necessary
For gear event, craft new gear whenever gear event is not running and then do upgrades when event is on. Now that elite is craftable, the ability to select shards instead for Altas season gear lines is an attractive option
Mehaten is a popular perch dragon as it’s the lowest tier mythic warrior, so fire gear. The warrior class’ perch boost is generally considered the best from what I have seen, ranking even legendary warriors over the mythics from other classes. Some people choose to get a mythic seasonal dragon so they can evolve it as their perch allows but this is not realistic for a lot of players. If you aren’t able to get enough pearls for your perch to keep up with the rest of your towers it’s fine to stick with a lower tier dragon. Earth is also not a bad choice as iirc it’s used the least as a secondary element for other types of gear
Shards I already covered. For good glory learn what makes a good matchup for different primes by looking at their stats. E.g. attacking a destroyer using a trapper is usually bad because a destroyer has moderate defense and a trapper has low attack. Also remember that while you get glory based on your kill ratio, it is capped by 1.5x the number of troops you lose. So while attacking an enemy sieger with your own sieger is a good way to lay down the hurt (high kill/death ratio), you won’t get very much glory for your effort (you will probably reach the 1.5x cap but get a small amount of glory each run because you lose so few troops)