How to progress 4* to 5*?

Kjempen

I have around 30 four stars champed. No 4* is missing a cover except for Cloak and Dagger. What should be my next step? I don't really have any usable 5* yet. Have them all with a few covers each, only a couple of them missing a color in their powers. Should I just keep champing 4*s? Should I hoard cp and buy 5* covers, or should I just keep pulling cp and LT? 
My best covered 5*s are:
Doctor Strange (3/2/4) - one more blue would be good
Black Bolt (2/3/5) - one more green would be good

Magic

Same position as you are so I have already give this lots of thinking. First question - do you really want to go into 5* land? It is said that such a move limits your roster versatility and makes the scaling in PvE pain. But PvP is easier in terms of climb to 1,2k (or maybe not even as some report). 

Now if the answer is still yes then the overwhelming majority of players suggest hoarding LT and CP. But not to buy the covers - to open them all at once on the Latest Legendary store and cover 3 latest 5* to a max. Benefit of doing that is that customer support still offers the chance to swap duplicated covers. How long this service will last nobody knows. 

You need anything from 250 to 300 pulls to be sure to cover the 5*. It could be advisable to favorite Bolt or Strage when you do that for a chance to cover them as well. That way you could have 4 or 5 workable 5*. Add couple of millions of iso and you are good to go. 

Buying covers with CP is way to costly. It might make sense for the 13th cover when you have some others dying on the vine. Otherwise I would no go there. Also opening LT and CP as they come won't help you as the 5* land in classics is way too diluted and Latest are more expensive. 

For the time being my decision is to hoard and keep championing latest 4*. I don't touch Legendary tokens at all (65 and counting). And CP - i use on classics till I get another 4* to max covers and then it's back to hoarding. This might slow down the overall process of hoarding but it will put me in the best position when I finally open the pack (again you need loads of ISO not to waste covers when you open 250 legendary tokens). 

Quebbster

The best move is probably to hoard legendary tokens until you have around 300 or so and then opening them all in one go so you can get the Latest Legends fivestars fully covered at once. You could set Strange and Bolt as bonus heroes and hope you get their covers that way.

Kjempen

Thanks for all the tips. I kind of have a plan now. And yes, I want to move into the 5* tier.