I use my HP to purchase Supports. Right now I am saving 50K HP for the X-Mansion, but it’s taking too long so I’ll need to buy several Stark salaries. It will be worth it because it grants all X-Men a +1 AP at the start of each turn. If I equip it to Gambit he starts the match Invisible for 5 turns. Totally worth it.
Only 5 turns? You need WAY more levels on your X-Mansion, Punisher… 
Shields and slots, same as most I imagine.
When I get enough of a surplus I’ll buy a HfH deal or a 40-pull from a vault.