Whether to upgrade with additional solar array or additional (fortress power) battery.....

Seems like a simple question but.... we're entirely off-grid, powered by a single large pole-mounted solar array and 18.5 Kwh Fortress Power Lithium battery. 2 or 3 days without sunlight and the generator often goes on. On multiple sunny days, the Lithium battery will be at 100%, by early afternoon. At the same time, on partially sunny days an additional array would charge the single battery faster. To diminish any use of the generator, ideally we might add an array and a battery, BUT..... finances for now dictate either doing nothing or choosing between adding a second array or a second battery.
Any suggestions on how to tease this out, are there significant pros (or cons) to one choice over another. Do you need additional data to help us decide?
Many thanks for any help.
Charlie

Yeah, how many W of PV panels?

What is idle consumption of inverter?

What do your loads come to, in kWh/day?

More specifics like Hedges asked and we can help more. But entirely off grid - how often do you have your batteries at 100% and all your extra power is going to waste? If its multiple times per week I would lean towards getting more battery. Expanding your battery will also let you increase the charge/discharge rate of your battery which may be beneficial.