This is easily broken. You have far too much control about the trigger condition and easily find a card that lets you pay life multiple times a turn.

Best case you could check for the first time you lose/pay life each turn. This would make the timing awakward, but you could have:

"Whenever you lose lose/pay life the first time since the beginning of your most recent turn, put a blood counter on ~.

Remove a blood counter from ~: Add or to your mana pool."

This would allow for a controled outlet of mana. Would also fit better with the name since "investment" has a connotation of "longterm".

okay i like that. Why did you lower the mana amount tho? The reason of easily breakable and too controllable doesnt mean its plain OP, if it please tell me but until i can be sure Im gonna keep it att bb or rr