I think AnotherInkling's advice is good: Start with Doug's suggestions for "Don't leave home without it" gear.

Then, If you carry a briefcase or bookbag, consider adding a small first aid kit such as an Adventure Medical Kits Ultralight .5 and maybe one of Doug's PSKs and an inexpensive emergency poncho. Those three items would give you a lot of utility in a fairly small space.

From there, a zillion different directions you can go. You might want to do some searches on this site and see what people EDC (everyday carry). You'll pick up a ton of ideas.

Once you've got your EDC where you want it , you can start thinking about home kits, car kits, BoBs, etc. Warning: It can get a bit addictive, but it's fun.

There's no real deadline ... just increase your preparedness a little bit every opportunity you get. Next thing you know, you'll be thinking about upgrades.