The one 6* will help you progress the most everywhere.

I actually do have a great farmer, Athel at 60, only needs scrolls and  banner. She can farm 12.3 or 6 at ~25-30secods depending on how strong the food becomes..

Let me see if I can figure out how to post my roster:

With the champions you have now, I'd advise to get Tayrel and Steelskull to level 60 and use any epic books you have on Tayrel, at least until his A2 is maxed. Though maybe indeed start by getting Steelskull to 50 first. Apart from them, I guess it's mainly for your clan boss team that you'd want to take some level 40s to 50: Frozen Banshee and/or Occult Brawler, Bulwark, Coffin Smasher. And High Khatun at some point but it may not be very urgent, depends a bit on how easily she is currently dying. 

As for gear - don't get too hung up on people saying this and that is trash, you should only be using X star pieces, all boots must be speed, etc. You just use what you have as well as you can. Even if they're non-speed boots, or a flat stat chest that happens to have great sub-stats, non-matching sets, whatever it takes (that last one is something even high level players do, because on high level gear, the set bonuses pale in comparison to the stats of the pieces in many cases). And obviously when you get better champions and can upgrade, e.g. from Warmaiden to Tayrel, make sure the obsolete champion doesn't still have gear that you could better use elsewhere. 

You'll mainly want to farm dragon early on for gear - the good news is you have quite good champions for dragon already. Tayrel, Athel, Steelskull, Coffin Smasher and Frozen Banshee could get you quite far, for instance (although FB does need to be booked if she isn't yet). 

Gems are few. I 'like to' save them up to buy a 1 or 3-day DXP, or use them for energy packs when I'm super close to leveling something up and I can't (psychologically) wait for the energy to tick back up, particularly when a DXP will expire. ;-)

Otherwise, I run a really gem-poor ship unfortunately. I saved 500 tobuy into the mine, which I regret horribly. I have been "shopping at Mino's" for a while now, but only less than half of my main champ's scrolls have been booked, I think only the first two levels (work in progress),  Athel, Tayrel, WM, and Spirithost; and I've spent a lot of time there. It just takes a long time (at Stage 11) but I likely wouldn't be successful if they all weren't there together.

Thanks for your help and the good direction! I am going to 5* steelskull first, then attempt to 6 him and Tayrel (Tayrel first to 60). I do use books, I don't have many, though I've put quite a few into Tayrel, but only one landed on his A2. of course! Frozen Banshee's not booked at all, I don't think. But I would like to bring all CB champs up to 50 and eventually 60.

My main worry was super focusing on one champ at a time to 60. But bringing up a team sounds much more appealing to me.