First you want to find inverters that can power the stuff you want. They don't all work with inductive (motor) loads, and don't all put out pure sinewave (which some devices require, ro at least operate much better with) so you have to list your requirements, then find the inverters taht will definitely do those things, and are rated high enough output to do them for as long as you need them to (assuming your battery will last that long).
Then you look at the inverters' iinput voltage range. Some work on "12v", which is usually around 10v-15v tolerance. Some work on "48v", which is usually around 45v-55v ish, but could be a wider range. Some work on other input ranges. Not all the input ranges are really compatible with the voltage range you get out of every type of battery pack, without imposing odd limits on how full you charge them or how empty you drain them.
THen look at what you can build out of the batteries you have (or will get). If you're using non-LiFePO4, whcih is most likely, then there aren't any good configurations that work for 12v systems. You either have to build a 3s pack that doesn't let you use all the energy at the lower end (early cutoff for discharge), or you have to build a 4s pack that you can't fully charge (or risk damaging the inverter input).
48v systems are much more likley to have an input range compatible with the full and empty limits of a non-LiFePO4 battery of that voltage (usually 13s).
Then look at how much current the inverter needs to do the work you're asking of it, and how much current each cell can output without voltage sag (staying well within it's C-rate limit, not pushing it to it's edge).
THen look at how much capacity each cell has, and how much capacity you'll need to do the work for the amount of time you need it to.
Then determine how many parallel cells it will take to provide enough current ot the inverter to do the work, for the amount of time you need it to do it.
Once you have all that info, then you can build the battery and get the inverter, and test it all out.
Then you can look into portable charging options (like solar), if you need more time than you can carry in a battery. Often it's easier (though not necessarily cheaper) to carry more battery than to carry the solar panels needed to recharge it in the amount of time available to do so each day.
You may find that it's easier (maybe even cheaper, but probably not) to get low-voltage-DC-powered appliances than to build and carry battery/inverter to power AC types. It's probably more efficient to do that (no losses from converting to AC, and then back to whatever the device uses inside).
THen you can still follow all the steps above, except you repalce the word "inverter" with "appliance" of whatever type it is.
There've been a few threads about similar stuff, but harder to find in a search because different people use different terms.
ONe that has some info that may be useful is this
https://endless-sphere.com/forums/viewtopic.php?f=7&t=12667&hilit=camp%2A+power#p188543
This is a search that might find other useful threads, but there's a lot of irrelevant results too
https://endless-sphere.com/forums/search.php?keywords=camp*+batter*&terms=all&author=&sc=1&sf=firstpost&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
Some of the stuff on "solar charging an ebike" is also applicable, as are a few other topics about portable power and inverters.
