Realising that there is stuff to learn is the biggest hurdle!
I will usually be able to answer stamp questions but I started collecting when I was 7, my father ran a stamp shop and I only stopped collecting in about 1998.
I don't, of course, know everything but, between us, the stamp sellers on here can probably teach you what you need to know.
2nd lesson for today - definitives with this portrait on them are called Wildings (again, after the artist who was Dorothy Wilding