Triplanetary, despite being the first in the Lensman series in internal chronology, is a fix-up of short stories and was put together quite late in the series, so it's very much not the place to start. The place to start is Galactic Patrol.

I love Smith dearly, but I grew up on him; I can't remember not having read those books, which means I hit them somewhere before age six. I have less than no idea how he holds up nowadays.