In Polarity’s guide you’ll learn that in the beginning of the game you should spend HP on roster slots only. And I would agree with that, but it has limits (I would say 15 slots +/-). I learned it is wise not to do this anymore if you wish to enter the 3* land quickly, I am sure that you need to stockpile HP for buying specific 3* covers instead. And here’s why:
The amount of new characters released is now just incredible, it’s not really worth anymore to collect all 3* characters and block slots with them being constantly under-covered. I believe you have to make a decision pretty early. That key question would be - "which five to seven 3 characters I wish to keep and focus on in the long term?"* The immediate counter would be why not to keep only 3? Well, you never know how nerfs and buffs will affect your characters, it’s good to keep your roster slightly wider, to enable a quick replacement. But why not more than 7? Just because even if it is tempting keep in mind that when each new slot will cost you 500HP (later in game) for those 3 slots you can guarantee-buy 1 specific new cover, that you need! And buying specific needed covers gives you an incredible edge and advantage in your transition.
My real life example - I had Hood residing for nearly 150 days in build 5-3-4 - which is not making him good at all… I bought 1 blue cover, making him 5-4-4 and suddenly he become a bit more useful. Within next 2 weeks I stockpiled additional 1250 HP and bought additional blue cover, respeced him to 5-5-3 and that guy is a monster, helping me significantly in achieving further HP and ISO for building other characters even if combined ‘only’ with 2* Thor or Wolvie. In this example, the same would apply even if he was only 1-5-1 because his strength lies within his blue ability.
In order to stockpile HP I recommend following:
- Do NOT invest in shields at all (unless you need to climb over 600pts per PvP, which is not really easy in case you don’t have few 3* maxed anyway)
- Do NOT invest in more than 15 slots (trust me, I have over 25 slots occupied by characters I don’t use regularly either because they’re weak or significantly under-covered, return on such investment is low)
- Do NOT buy health packs (just don’t)
- Do NOT buy tokens (the odds of getting your needed cover are so low, that it doesn’t make sense)
- Do NOT spend HP on other things like returning a char from patrol…
- Go for HP progression rewards (at least up to 400 pts in PVP)
- Participate in PVE to extend which allows you to get at least the lowest possible rank granting HP (subs are very generous often)
- Check your prologue missions - didn’t you miss some nodes rewarding HP?
- Play at least once a day a mission (even if you don’t have time, play 1 easiest/quickest prologue mission) to get daily rewards - occasional 50HP from daily random reward is just worth it
- Join alliance if you don’t have one yet
Example of covers worth investing HP:
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Hood -

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Patch -

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LThor -

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LCap -

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Punisher -

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Deadpool -

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Luke Cage -

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Blade -

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Black Panther -

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Doom -

even if those characters are on lower level (understand less than 166), those key skills make a real difference as often they are not dependent on characters level and still have powerful attributes! And I am sure there’s more to that list than I just mentioned.
People will tell you: “wait before buying specific cover until you have already 4 of them”… but you could also wait for ages (given the token odds, top PVP/PVE ranks competition, vaulting characters etc.), it’s just not worth it.
Mods - before moving this into tips and guides, keep it here to see if there’s general agreement or not.