What I would recommend for a budget conscious first water filtration system.
If you want one of those pricey systems but can’t afford it, you can actually build your own version of a gravity filtration system. All you need are some basic tools, a couple of food grade buckets, and 2 or 4 Berkey filters.
I have not made this myself but have been present when someone else did, and it absolutely works like a Berkey. We did the dye test after he made it and the DIY system passed. This is a good short term solution.
When you can manage it, I recommend upgrading to a ready-made high quality filter made with stainless steel, but this will get you through in the event of an emergency.