Some stuff we all already have, we can build toward further capabilities. I assume a stay in place scenario.

Skills trump things.

Physical and spiritual/psychological strength is imperative

• Water and rain catchment; Water purification (not just a filter, it needs to be purified)
• Food: start with grocery store canned - it is what you already eat (important!) and freeze dried is too expensive; start small and work up, don't try to buy 6 months of food all at once
• Medical and hygiene (personal and environmental): more people die of disease than direct combat in a war zone/grid down; get trained on your equipment. consider whether you want to add alternative medicine skills (esp herbalism)
• Power and heat: fuel, generator, solar battery, propane, seasoned wood; heater, camp stove,
• gardening: focus on stuff you eat and prioritize high caloric density and high micro nutrient plants. Learn to preserve your harvest.

THEN, as you are able

• Firearms as you are legally (?) allowed; recommend sidearm and long gun for each adult AND TRAINING!!! If you anticipate any hunting, consider an air rifle - not on the registry, cheap to own/operate/ train, good for marksmanship fundamentals training. good for mall game hunting (depends on your caliber)
• stack ammunition deep...recognize the need to training, possible hunting in addition to what you allocate for protection....training will be significant
• Repair parts: especially for home/shelter...nails, screws, Duct Tape, glue, plywood: also small engine parts and maintenance....POL, belts, machine screws, spark plugs, WD40; manual tools (both carpentry and mechanics)

THEN, when you are satisfied that you are reasonably sustainable,

• continue to add to skills and things
• start adding PMs. Silver is more easily used than gold, especially "junk"silver. Gold is a better sore of wealth, but silver is a better choice as a medium of exchange

don't get overwhelmed...prioritize and build a little at a time. Make training fun