So I just did a tier 6 sacrifice with my last 8 non-essential 4* characters and got 2 skill shards. Bummer.
But while I was glaring at these two shards, I had an idea. After doing some math, I found out that in order to achieve an exalted sacrifice with common 3* characters, you must apply 4 skill shards to ten of them in order to boost the numbers up to the requirement. Since it's typically more difficult to pull at least 8 4* characters for a proper sacrifice, I decided to give this alternative method a try starting today. But 40 skill shards is certainly not an easy task. From what I understand, if all of your troopers are consistent as are you, you can get 1 skill shard every other day. Add the one you get from the arena, that's an estimated 4.5 skill shards every week, not counting skull quests. So it could take approximately 2 months to get all 40 skill shards with these conventional methods.
As for the more familiar way, pulling 8 natural 4* toons isn't exactly easy either. Rare souls are somewhat easy to happen across, but they don't come as often as one would like. Especially considering that the chance of getting anything above 3* is what, like 10%?
And now legendary souls. Well the best way to get one is by forking out 1000 arena coins, now that's simple because by playing consistently, you can make more than that in a week. Problem is, that you only buy one legendary soul a month. In my opinion, that's kind of depressing. If they were reduced to 1 or even 2 weeks between purchases, it would make things easier. Due to events like the one we just had a few weeks back, the number of legendary souls available shot up immensely. But that was only for a week. And by now most people have finished their 88 missions by now, and they give you enough shards for 1 legendary soul.
Now there's event souls, like the ones we've been having. Earn 200 fragments from the Lord of Light dungeons and get a free 4* character of the devs' choosing. Since they haven't been the best toons around, the selling point of these imo are the fact that you can save them for a big sacrifice. But shards aren't easy to get and you need alot of ironite to get them. Since my method of spending is to just save ironite and to NOT waste it on rare souls (we've all been there) it's nice to get these events and have a decent stockpile of ironite to throw away. How I've handled these events is that I organize a team that can handle floor 10 on auto, so that I don't have to do it myself. It's like watching water while it boils, it's gonna take longer while you stare at it. So after a while you get your first soul. So after about 7 more of that grinding, you're ready for a new sacrifice.
So to sum up all that I've talked about, getting a high level sacrifice requires high level characters or at least alot of skill shards. As far as I know, the quickest and easiest way to do this is from character fragment events. So save up that ironite and assemble your death squad. Chances are, next time we do this, it'll be in the Gunner or assassin dungeons.