The Foxeer Wildfire is an excellent module, its $90 but performs easily as well as Rapidfire which is $120 according to most testers. There are cheaper options, but many of those are not great and around $50-60 anyway so spending a bit more is worth it. You will want a pair of antennae, I use a patch and a mushroom, both from Menace Rc. Lumenier antennae are very good, I can’t remember which other patch is good.
I have the Skyzone 02C, that has no front camera but has DVR and comes with inbuilt diversity receivers and is easily as good as my Dominators, certainly much better value. Plus they have a power on off switch, which none of the Fatsharks have. Buy the 02C if you want a Domoinator/HD equivalent with a good diversity set up.
Battery wise you can run two 18650 cells in a box or I use a 2200mah 2s pack on a lead, I put it in my pocket. The lead I made but they sell them. Fatahark uses a 2.5mm laptop plug on the goggles end and then I put XT60 on the other end. I added a pair of balance connectors to run the fan.
I wouldn’t buy a set of second hand goggles without at least a battery holder included, unless they are very cheap.