You could start with a 12V battery to learn. RV house batteries are rated in amp hours - ie Ah. The typical 12V car battery which is not deep cycle is about 80 Ah or 160 Ah for 2. 6V golf cart batteries GC2 are 220 Ah and 2 in series is 12V, they are deep cycle and just so you know a Marine deep cycle battery is a compromised starting battery.
GC2s are 1" higher so check your battery space. Until you start using the RV one can only guess the usage and what you need for batteries, chargers, solar, etc.
