Thanks BeefSupreme, it seems like I can't get the skipping FGs aprroach for a sometime
There is almost no point where it's not advisable to skip "unwinnable" FGs. The most profitable FG decks are so profitable specifically because they efficiently beat the gods they can beat and ignore the rest.
With that being said, there are decks that have a chance against every FG if you find skips to be so abhorrent, though they are generally quite slow (due to the need to control the battlefield against any type of opponent) so they are not the most profitable. Additionally, they are going to pretty much require being fully upgraded.
Also, note that most of the decks with "skip" FGs are welcome to play against those FGs anyways - some of them even have a 10-20% win rate (or even higher) against the "impossible" FGs. However they are listed as skips because it simply isn't profitable to play the games against them if your goal is the most profit over time. This doesn't really apply to any of the unupped ones, as the unupped ones pretty much all have situations where they basically cannot win (i.e. any opponent with the ability to destroy/bypass shields for LS/firecell, any opponent with field-wide creature control for RoL/hope).
AI4 is a wonderful place to farm at the pre-fully-upgraded stage. It's either nearly as profitable or more profitable than the unupgraded FG decks, and doesn't come with the requirement of skipping some FGs and playing exactly the same game against the rest - the random opponents mean there's a lot more diversity.