OK, so a (very) rough calculation then, fridge 25 amp hour, lights say 3 hours, 3 amps total draw say 10 amp hours. That's 35 amp hours per day. So that's a min 70 amp hour battery - I'd go for a 100, provided it will fit in your battery box.
Also, consider your charging - the last 20 percent of charging takes hours. Many cruisers only ever charge to 80% for this reason, unless on shore power. The 100amp hour battery gives you that ability.
got a new 120ah battery today ,so will be taking care of it,no cranking,have a good crank onboard.