You need to look at your power consumption habits when dry camping and determine if you are OK with a generator or solar to recharge.
We do fine dry camping for 2 weeks at a time with a well maintained single Trojan SCS 200 12V battery (115AH) but we do run a small quiet 1kW generator every morning to maintain the battery charge. We do not use an inverter but do run vent fans all night in the summer.
Many people conclude that a single 12V batery will not work for them based on a bad experience with a generic 12V battery that has been allowed to sulfate and lost much of its capacity.
If you are going to run an inverter then you probably will need multiple batteries.
Dick