Do you need primers for makeup?

I don't normally wear a lot of foundation, and my skincare routine is usually just cleansing, toner and moisturiser and sunscreen in the morning.

Do I need to put primer before foundation? I usually only use my foundation as concealer, as in I don't put foundation around my cheeks, just my forehead or some discolouration on my chin and slightly side of my cheeks.

I am just wondering if primer is necessary before putting makeup on? I often get mixed answers to this because people either say you need it or it's actually not necessary. I'm quite cautious about adding new product to my face as my skin is very sensitive and break out easily.

Any recommendations for primer? Or any other alternatives?