Out of the heroes you’ve listed, these are the only ones deserving of you mats as soon as possible:
Vivica, Sartana, and Rana.
The rest of your 5* I wouldn’t bother with unless you decide you love them and want to take them further. Especially Aegir, since the opinions on him are so mixed, you might have to figure that one out for yourself. Elkanen is considered alright but not great, and Elena is along the same lines as well (though, I like her better than Elky- her attack stat is super high and she has riposte).
Now, out of the three I listed I would obviously do Sartana to have a purple 5* maxed- she’s a great fast sniper. For yellow, now that depends on your priorities and roster. Vivica will be more of a utility hero, helping out your entire team so that they can live longer (since her special isn’t related to stats, she could stay at 70 and work just as well- only thing is she’ll be squishier). Now Rana is a solid defender and I wanna say a great attacker too (though, I very rarely see her), but in order for her attack and DOT to max out, she needs to be taken to 80 to reach full potential.
Overall, ascending Rana to 80 has more benefits since it increases her damage output. Whereas, ascending Vivica to 80 has more benefits when it comes to helping out the rest of your team live longer. So, I’d ascend whichever one fills more of a role that you desperately need on your team. If you don’t have any healers or cleansers leveled, Viv. If you don’t have a solid tank or splash attacker, Rana.