I am not about to claim hat Wittgenstein is easy understanding, and I too would argue that On Certainty is a good place
to begin; however, part of our difficulty lies in our thinking that philosophy, if it is anything at all, must be about deep stuff.
It is better to think that it is about stubborn stuff. Some good companions to Wittgenstein's work are Rush Rhees', articles,
Wittgenstein's Builders, and Can There Be a Private Language?, both found in the book Discussions of Wittgenstein.
There is also, of course, Norman Malcom's, book Wittgensteinian Themes--with emphasis on the grammar of 'thinking'.
One might memorize the passages on page 19 in The Blue Book (It begins with 'If we study . . ." and ends one paragraph
later on p.20 with "to enumerate cases of knowledges.") The Malcolm piece on 'thinking' is good to hold i conjunction
with this last from The Blue Book. The voyage is worth the struggle . . . but gets a bit lonely.
Remember that W. was not pretentious.
Again . . . best wishes.