I'd go in this order for obvious reasons.
1: Devouring. Directly the most OP of all qi types, devours all and benefits you, whether it is merely rocks and dirt or the blood of god, all of it can be used to benefit you.... Seriously, by using devouring qi you can even convert rocks into nourishment for your physique and the average meal into a qi elixir........ Plus devouring souls of your enemies gives you near unlimited knowledge and techniques, making you into a master jack of all trades with no weaknesses what so ever.
2: Blood. Again, every living beings has blood of some kind, blood is the foundation of life, with cultivation I could easily take the essence blood of my victims, whether they be beast or man, nourish my blood which will strengthen my flesh, bones, and tendons, not to even mention how it will leave me vigorous and give me power regeneration, to the point I could just leave a drop of blood somewhere and 90 years later use that drop to rebirth myself. Not only can I gain strength from killing, but life itself. Almost every novel ties blood essence to life force in some way shape or form, thus my constantly nourishing and tempering my blood cultivation I will effectively be immortal even if I don't work hard at all. Hell I could even use blood qi to temper my soul and fuse my soul to my blood, effectively becoming an immortal blood demon that can have any body I wish and even if the body is crippled trash merely killing a few beggar slaves would fix me up, I am literally a master of disguise with no equal, unkillable, and even if the world tries to destroy me by teaming up against me I can survive in another persons body with no repercussions other than having my cultivation weaken, but as a blood demon my soul would be incomparably strong making killing anything I want incredibly easy thus allowing me cultivate to any level quickly....... Plus Blood is of the Yang element and a Blood Demon would fall under the Yin element, thus giving me both the properties of yin and yang, thus allowed me to have all benefits with none of the drawbacks, like a vampire that walks under the sun without worry, I could weather thunderous storms of both righteous and evil paths without worry, even heavenly tribulations wouldn't pose a threat to my soul.
3: Some kind of pure adaptable qi that can be given to others.... This one should be really easy to understand, imagine starting a small sect in mortal lands, giving your qi and cultivation to other, only to let them cultivate with all their heart and once they reach a powerful enough state you then recover what was once given, but since they used it as their foundation you also take what they've gained with it as well. The idea of going to a cultivation world and letting others level up for you is just intoxicating in a way I can't even explain. (PS: Obviously after taking back what was given you must kill them, otherwise if word got out you'd definitely suffer horribly.)
4: Spacetime. No reason to get to specific with this one, shrinking space, developing realms at higher levels, using the power of time to fight others.... Everybody should already know why this is powerful.