To turn off ads and offers, open Options > Preferences > Advanced. Here you'll find a large list of flags for the app and a filter box. Search for and disable the following flags:
offers.left_rail_offer_enabled/left_rail_offer
gui.show_plus_upsell
offers.sponsored_torrent_offer_enabled/sponsored_torrent_offer_enabled
bt.enable_pulse
gui.show_notorrents_node
offers.content_offer_autoexec