Thirding this, having a clearer idea of what kind of stuff you are going to print will help you a TON.
That's why I would suggest to dabble into modelling for a while first, see what kind of stuff you find more interesting/fun to make, and dial in your decisions from there. I say this, OP, because I was in your position of thinking about doing both resin for miniatures and FDM for buildings/dioramas/useful things... But I ended up doing mostly miniatures, because that's what I found most fun to do. So I would have been better served investing the FDM money in a bigger and better resin printer.
For software, since you mention that you may get a resin printer, I assume you are considering eventually making miniatures, characters, monsters, etc. If so, you will want to look into software that has sculpting tools. Blender has them, Fusion 360 as well, there are many others. I use ZBrush but a lot of people find it weird to use. Blender would probably be the best starting point because it is free, extremely well documented and has everything you need.
As a last note, if you are not familiar with this world, you should know that even with the best of printers, you should expect to spend a lot of time tinkering, troubleshooting and tuning. If your expectations are to assemble it and immediately start printing cool stuff, you will need to adjust them. It is a really fun hobby, but requires you to be willing to deal with days in which your prints suddenly come out wrong and have to spend the whole day debugging the issue instead of having fun.