Ah okay. Another thought too of course is to wait until strike - Premium = Fib Level and do it on weeklies. Just making up numbers in this example to show what I mean.
Instead of selling the 121 put for $4 since 121 is the entry price you want, how about selling when the strike - premium = fib level.
Like here's a real time example
November 25 (weekly) SPY 122 put you can get 1.89 for. If you get exercised you get in for less then your fib level at 120.11 and if you don't get exercised you're picking up money while waiting for it to hit the fib level. Since you want to buy SPY at 121.06 anyways, this seems like a pretty favorable option for you.
In the above example we would have waited too long to sell the put based on my thought since our strike - premium is about $1 below the fib level, so in the future you would be selling the put sooner obviously, in which case you'd already be pocketing cash.
QUICK EDIT:
Forgot something though, if you truly believe in magical powers of Fib, then maybe this won't actually work

If you sell a put at 122 and have a purchase price at 120.11 if you do get exercised, let's say SPY closed at 121.85. You are in for better then your fib level, and you are technically ahead of the game, however one important factor is missing, it never actually hit the fib level

haha