Hi amindu,
If your mattress is still in good condition and there are no soft spots or sagging (either visible or virtual) then a topper can certainly be a good option to add some additional comfort and pressure relief.
There are many unknowns and variables involved that can affect the type, thickness, and firmness of a topper that will work best for you on your mattress including your body type, sleeping position, your preferences, your sensitivity to different firmness levels, and the specifics of the mattress under the topper (a topper will feel different on different mattresses) so it’s not really possible to predict with certainty which topper would be the best choice for you because each person can be very different.
Having said that … post #2 here and the topper guidelines it links to have more information that can help you use your sleeping experience and along with your familiarity with different materials and other criteria that may be important to you (such as the return policy) as a reference point to help you decide on the type, thickness, and firmness of a topper that will have the best chance of success.
If you are looking for “a little to a fair bit” of additional softness and pressure relief then a 2" topper would be a likely choice “on average”. If you are only looking to change more of the “surface feel” of your mattress and only need “a touch to a little” additional softness then 1" would be the most likely choice. 3" would be more in the range of “a fair bit to a lot” and sounds like more than you would need.
Phoenix