The best way to get a character save up x amount of cps and legendary tokens or buy them packs as you get them.
And which pack do you get Classic or Latest or The one containing the newest 5 star like sanctum sanctorum dr strange pack.
If you choose save how much should you save?
It depends.
There is no best way in general. If you already have the chars in CLs at 6-7+ covers go for them, don’t save, open them now. On the other hand, if you all your 5s have a very small amount of covers, then save and go for LLs when three decent 5s are there . etc. etc.
Totally depends on your starting point.
If you are a brand new player, I would say save all your LT and CP until you have pretty much all 3stars champed and are starting your 3-4 transition with plenty of HP to spare for slots and then blow your enormous stockpile on Latest LTs. With CP saved from a year of play (getting decent results) you could cover all those 5s in one go.
Only thing is you have to hope and pray those 3 lastest legends aren’t poor compared to the majority of the 20 5stars that will be in Classics by then.