Charging a Battery Bank

I bought the Champion 75537i 3100w starting/2800w continuous inverter generator. I couldn't justify the price of a Honda or Yamaha. SoundGuy....It's true that we have only camped at State Campgrounds and Private campgrounds where electric is available and we have a trip planned where electric is not available, but I'm also thinking about the future. I will be retiring in a few month's and my wife will be retiring at the end of the year. We like the idea of being able to do some traveling where we can dry camp more as well. If 2 6v batteries is all we need, then 2 is all we will buy but right now, I have no idea how much power is going to be necessary. Our camper is a 30' travel trailer with all of the normal power options. Running the furnace at night, the fridge fan, lights, water pump etc. is what we'll be using. Generator times where we are going this fall is limited to 2 hours in the morning and 2 hours early evening. As I said, solar is something I'm also looking into but that's not something we will be doing now. I still don't know what type of charger I need. I understand I need something that is a smart charger and able to charge reasonably fast but which brands/models? It's very confusing and every manufacturer says there's is the best and I should buy theirs. Currently, I have a BatteryMindr 2012 for my 12v Marine/Rv battery but according to their website information, I can't use that for charging any type of battery bank. Other models they sell are capable but the one I have isn't. On the subject of batteries, I'm somewhat limited to which brand. I would like to buy Trojan's but after researching, no one locally sells them. The closest place is over 100 miles away from where I live. My options close by are the Duracell brand from Sam's Club or Interstates. I could order Trojan's online and have them shipped to me, but the cost doubles by doing that.