Do it bit by bit and do it wisely.
Try making a list of what things you want or need to put in your kit. (and what you already have or is around that you can use)
Then go over the list and work out the needs and make them a priority.
Also work out items on your list that are multi use and work out items which are specialized. Some items will be used in any disaster and some in only one type of disaster. So work out how you plan to use items on your list and then prioritise again.
When buying items, buy items that can be trusted when you need them. Quality doesn't mean highest priced. But if you buy an item and you dont trust it, thats a mental hit you dont need when the SHTF. Potentially worse is over trusting an item that fails because you didn't do your homework when checking in to it before purchasing.

There is a lot of good info here. But we cant give you specifics about where you live. So research your area and find out what you are most likely going to face. When we are born we are a statistic. So look into some statistics around you. Look at your country side and find out likely events. Look back hundreds, if not thousands of years and see what has happened around your area. The earth works on a different time scale to humans. Also check weather history.
It is better to know what you are likely to expect and make plans towards it.
Start basic and work up from there. It might seem daunting but adding bit by bit while working to a plan, soon brings results.

Some of the things I have found out for myself about my local area includes living 80km away from the epicentre of the strongest quake in Australia for the past 200 years. And also living a few kilometers away from Australia's youngest volcano, and then finding that its last siesmic activity occured in 1978.
I haven't specifically prepared for an earthquake (yet), but after receintly finding out about how big the quake was and that it damaged buildings in both Adelaide and Melbourne, (about 900km apart) Earthquakes has gone up on my priority list to prepare for.