I will say Gauntlet was initially fun for me and I am glad that others still find fun in it. But for me the rewards don't even come close to matching the time and effort to deal with the current talisman management system. I go as far as I can without switching everything around or until I get what I need to complete the taliman set or finish getting frags for the featured toon. All the other rewards are either pointless to me (heroic frags) or can be obtained easier/quicker elsewhere in the game.
Aside from Iron coins but odds are if you're reaching SSS consistently you only need those for the spending events anyways.
Talisman selection is the second most important part of gauntlet right behind character management (only because it determines which talisman sets you can use) so I like the idea of having some go-to talismans that you love to use but using a favourite cosmic might hurt you if it doesn't counter as well as one you don't like.
Ignoring ALL of that if you really just want a list of top 5 cosmics that I tend to use here you go:
- Serenity
- Alchemy (potentially haven't actually used it in gauntlet yet but I expect to like it)
- Sacred
- Steel
- Blight