Stop bashing the nice guy, he's just trying to help.
Back to the topic, "Dark Rush" has the best potential, but you do need to learn how the file works.
It's a lv2 rush that requires some thinking, when to let unit die off, when to boost with rats, when to succubus. It's all about timing.
"Natural born killer" on the other hand is a more standard lv3 rush, its the base of my 1st folrart file and got me from 40% -> 52% win rate.
But I doubt it can go any higher than that without tweaking (I don't know, haven't touched it since then).
I would say focus on one sphere first tho, unless you have deep pocket or there's a good offer.
Ah... Everything's about MONEY, now that makes much more sense...