Atangana would be a really smart signing for reasonable price. He is 20, similar type like Gana, could learn a lot from him to hopefully slowly take over the position as Gana ages.
Hope we can also sign some additional backup players without a contract - likes of Woodman as a goalkeeper, Tagliafico as a left back to compete with Mykolenko. Or even still KWP to compete for starting job on both LB and RB. Coufal as a backup for Tete would not be the worst signing either, Patterson really needs to go on a loan our be sold. Would not mind Brownhill or Pasalic to expand the midfield options either. If not possible, try to loan in some alternatives.
Any big spending has to be for new attacking players or big talent.