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 and disable the following flags:

offers.left_rail_offer_enabled / left_rail_offer
offers.sponsored_torrent_offer_enabled / sponsored_torrent_offer_enabled
gui.show_plus_upsell
gui.show_notorrents_node
bt.enable_pulse
offers.content_offer_autoexec