I would start with skills and PERSEC.
Preppers so quickly get caught up in trying to buy their way to a sense of security, but a closet/room/shed full of gear isn’t going to get it done.
Of course, get a basic food and water supply up and running and budget money towards building it each month. Go slowly and use the food you store.
Pay off any debt ASAP. Live below your means.
Get a membership to a gun range and USE it. Become proficient with your firearms. I’m amazed how many folks just buy a couple guns and check defense off their list.
Stay active or get active and never stop. Mobility is so important. Walk as much as possible and do squats as your bare minimum. My husband is way more ambitious than I’ll ever be when it comes to fitness (he has to be able to carry adults out of burning buildings) but maintaining the ability to walk long distances and squat to pee are two things I intend to be able to do even when I’m a little old lady. That’s actually pretty ambitious now that I think of it.
Breastfeed that baby. Obviously, Dad can’t do that but he should move heaven and earth to support his wife in that. Breastfeeding is the most basic and powerful prepping you can do to keep babies/toddlers safe. I won’t bore everyone with details on that, but truly guys care about this. It’s a little awkward to talk about, but this should be an area of prepping that you don’t ignore if you and your wife/girlfriend are still in a fertile stage of life.
If you really want to be prepared for a long-term scenario and are prepared to do the work? Start living and learning now. Don’t wait to try to grow food. If you can’t move yet go ahead and start a container garden. Do something. Do whatever you can do where you are at. Take up hiking/camping/backpacking and use the excuse of that hobby to gain experience. All the camping gear in the world is worthless if you don’t know how to use it. You don’t want to try to learn things under stressful conditions.
And don’t get so excited you tell everyone you know. That is really difficult for a newbie, but spend some time reading about the gray man concept and apply it to how you talk to people, how you store your preps and how you go about making your home secure without making it look like you have something worth taking.
Working on my first cup of coffee, but right off the top of my head, those would be my priorities.