Opinions genuinely split on this, and the honest answer is "it depends on how and when you use electricity." A battery stores the solar you generate during the day so you can use it in the evening instead of buying from the grid. If your house is empty during the day and someone's home in the evening, a battery captures power you'd otherwise export for a few cent and lets you avoid buying it back at full rate later.
The other camp puts every euro into extra panels instead. Their reasoning: a smaller system already has high self-consumption, surplus earns money under the Clean Export Guarantee (CEG), and a battery rarely pays for itself inside its warranty. People who've run the numbers on their own usage often find a battery saves real money — but only if it's sized to their actual evening load and they shift charging onto a cheap night rate. People with low consumption or no evening occupancy frequently conclude they're better off skipping it.
A good rule of thumb: model your own half-hourly smart-meter data before deciding. A battery that matches your usage pattern can be transformative; one bought "because everyone gets one" can sit half-empty. If budget is tight, panels-plus-export is a defensible choice and you can always add a battery later if you fit a hybrid (or battery-ready) inverter now.