If running a genny is not an issue and you don't dry camp, get a good brands group 24 and call it a day. If you would like to have a little more juice before having to crank up the genny, get a group 27 which is a little bigger and will generally get most people a couple days if their electrical needs are modest.
Get a marine/RV Deep cycle similar to these. When I went to see what each had, the group 27 batteries were like $10-$15 more than the group 24's so I linked them. For a 3-5 year investment (depending on how well you take care of them), an extra $15 didn't seem like a bad idea to spend to get the extra capacity.
If it were me buying a group 27 in your shoes, I would likely pick the Duracell from batteries plus based on others feedback I have read on forums. I also would not be afraid of the Walmart selection as I have used that brand without any issues and it's a good battery for what you are paying for it.
BATTERIES PLUS https://www.batteriesplus.com/produc...UaAoAfEALw_wcB