First, do not attempt the Cantos without
this companion , and early Pound is a better place to start anyway. Personae features his earlier work--although even his early work can be daunting. Good thing with Pound is his work is published by New Directions (or as Pound called it, "nude erections") so it comes pretty cheaply. Also, read Hugh Kenner's The Pound Era for a great overview of Pound, his sources, and modernist poetry in general.
However, before getting into Pound, start with Frost (everybody does), move on to Wallace Stevens (difficult in many ways but he uses language beautifully), and throw in Elizabeth Bishop. From there, you can begin exploring.
I love the Romantics, Keats, Shelley, Byron, and Wordsworth, but they present more problems than the Americans.