I have 3 asparagus plants of about 2 years and I'm not getting a whole lots of spears. I don't know why? I only got about 5 spears the whole years.
None that you should cut - it takes a while for asparagus to become established and start producing properly - the crowns need to settle in and develop a good root system, so you won't be harvesting till the third year. The advice is not to harvest any spears which may be produced during the first two years, but to wait until the third year, when harvesting can be done for no more than six weeks from spring. In the fourth and subsequent years, you can harvest for eight weeks from spring onwards. Advice on growing asparagus here, particularly in regard to keeping it weed free and using fertilizer/composted materials, but the timing may be slightly different for wherever you are, this is a UK link https://www.rhs.org.uk/advice/profile?pid=310