The simplest and cheapest lockers are lunchbox lockers. Those are usually around $250-$350 each. You can do those yourself in your driveway if you are even a little mechanically inclined. If it's a daily driver, I'd probably only put one in the front since you're less likely to notice it in 2wd but it will be a game changer in 4wd. For an automatic transmission, it may be worth trying in the rear as well if money is tight. If you have a manual transmission, I'd avoid putting on in the rear because they just aren't very friendly when shifting and cause the Jeep to dart around as you get on and off the power. It's manageable and many do it but not the best solution for a daily driver.
You also have a full carrier locker like Detroit that are a little more friendly in the rear but still suffer from a little of the darting like above. These are much stronger though and cost around $700. The downside is, you will have to adjust the backlash on your gears when replacing the carrier so it's not super difficult for anyone with the right tools and know how but generally not for the average driveway mechanic.
The best all around is the selectable locker like the ARB, Zip, or Ox. These are all full carrier lockers and require some gear setup to install. You'll never know they are there until you turn them on but they are pricey at around $700 (Zip) - $1000 (ARB, Ox) each. Best solution by far if you can afford it. ARB and Zip are air lockers only. The Ox can be air, mechanical cable, or electric. Ox is the only one that comes standard with a diff cover and has a $25 optional extra of a drive-away lock allowing you to stay locked should you melt an air line or have issues with your air compressor.
