It’s better to understand what you’re praying than to mutter words in vain that you don’t know the meaning of.
Many years ago, one of the first things I ever learned thoroughly was the siddur and machzor. I went through all the tefillos line by line, learned the meanings of these prayers, perfected the correct phraseology of the words (listening to proper chazzanim), and went through a good perush on the tefillot. That has helped me enormously, and every summer, I generally do a study of the nusach for the high holidays and look through a good explanation of the tefillot so that I have better kevah and kavvanah.