The jury is still out of this. Yes, you should be familiar with the meanings of the cards. Yes, tarot is a like-long learning process.
But personally I disagree with the "start small" theory. Analogy: A pianist doesn't learn music by memorizing the names for each note. Neither do they learn by playing one note at a time, but a bunch of notes interplaying with one another; in other words, a pianist learns music by playing the music, not memorizing music theory. I feel that memorizing key words, indepth study into symbology is well and fine, but why not do this as you go along? Why limit oneself to one or two or three note pieces of music?
I learned both music and tarot similarly, slowly and with lots of music.
Even if you are slave to a book to decipher a Celtic Cross that seemingly has "too many" cards, and there are intricate meanings in the associations with the cards therein, you still gain experience reading large spreads.
My first spread was the Celtic Cross. Sure, I struggled, but this was part of the learning process. It wasn't as if I were reading professionally for another person, it was all in fun and in practice.
I definitely would not attempt large spreads reading for someone else. I feel this is the point at which you should stick with one or two or three cards. But reading for others is also crucial practice.
Everybody has their own personal methodologies, but I am definitely in the minority on this one --not saying anyone is "right" of "wrong," just giving my two cents' worth.
KK