The one gallon jugs are probably just for fermentation and not pressure resistant. That means carbonating in those jugs would create a huge mess when the pressure cracks the jugs open. If you ferment in one jug and transfer into a second jug with an airlock for long term storage, you risk oxidation (wet cardboard flavors), skunking from exposure to light and infections. If it was my beer and I hated bottling, I'd suck it up and bottle until funding permitted me to keg.
That is what I would do ideally. I can’t afford more kegs right now, so I wondered if there was any point in brewing a batch ahead and storing it mostly flat until a keg freed up... sounds like it’s not advisable?
Conditioning and carbonation aren't mutually exclusive time frames. As your beer is carbonating it is conditioning. As your beer is conditioning it is carbonating. Your yeast are living entities. They're swimming around looking for food to eat. Regardless of what container you transfer your beer to the yeast is still swimming around in search of food. Part of "conditioning" is suspended solids are settling out. That's going to happen while your yeast are still swimming around searching for food.
The key to successful brewing is doing everything you can to prevent your beer from developing off flavors or infections.
Brew your beer. After fermentation has completed cold crash your beer. Transfer it to your (pressure resistant) dispensing container and set it somewhere with steady temperatures.