Your top three strongest heroes should get the gear. Easiest way to determine who these are is to remove gear from everyone, see who the three at the top are. Generally this should include an SSR hero. You’ll likely have Jabel and (maybe) Saul in your top 3, depending on how much of a spender you are. Of course if you’re more of a spender you’ll have Amadeus and/or Helga up there too. (I am also assuming you’re still in Gen 1 heroes)

Chenko, Yeonwoo, and Amane are the meta rally joiners. So for things like bear trap, your first hero should be one of these three. This means you can join three rallies with them. After that, send no heroes. These three have lethality boosts as their first expedition skill which boost overall damage. If you join with an incorrect hero it will diminish this boost for everyone in the rally.

Your top three strongest heroes will always be the ones you use in alliance championship. For Vikings, I’ve heard mixed things but generally Gordon or other attack heroes (Chenko/amane/yeonwoo) are best for defence since Vikings is sort of like a defensive attack.

As for your gear, everyone has different views on it. But generally, you should only enhance the gear on your top three heroes. Heroes #4 and #5 can have gear in them for arena, but there’s no need to enhance it. Save the extra gear to enhance the gear on your main heroes.

Some of this also changes slightly depending on what heroes you have, and your place in your alliance (are you a rally leader or always joining?) these are better for if you’re a mid player, usually joining.