Waiting and piling up the cash in fiat before you buy is totally the wrong approach if you ask me because Bitcoin isn't a stable coins and you can't expect the price to sit around and wait for you to gather all the money first before you now use when you are satisfied with the money for investment. The right thing to do is simply to keep striving to accumulate just like you have stated with the little earning so that you can meet up with atleast the lower price because you can't tell when the price might go up or even down.
I have thought about doing this, with the income I have every month I will set aside some money to save and invest, of course not forgetting to meet my needs. Indeed, if you wait for the money to accumulate and then allocate it to Bitcoin, that's possible, but I don't think everyone can hold cash in fiat consistently, because there are unexpected needs or expenses and the money in the pile will always be used.
Of course, we won't know whether the price will rise or fall in the future, but what is clear is that we hope for the best, namely that the price will rise.