Clearouts aren't always the answer, neither is buying in bulk.
Our best season under Benitez was 2008/09 when we finished on 86 points and had our only genuine title challenge of the Benitez era. The summer before we had a relatively quiet one in the transfer market by Benitez's standards... to my recollection only Keane, Dossena, Riera, Ngog and Cavalieri were brought in for the first team squad the preceeding summer transfer window. Keane was gone by January, Dossena and Ngog rarely started, Cavalieri didn't play league games and really only Riera came in and played well regularly. Our team was relatively settled from the season before and I think that helped us have a consistent season.
Granted though, we had finished on 76 points the season before which was respectable enough, not the 52 points we have just finished on. This squad doesn't have as much quality as that one did, but I still think just a couple of shrewd signings is the ticket, then blood the likes of Coates and Sterling and we have Lucas coming back too.
3 signings maximum please - centre forward, winger, centre mid. I'd even have Aquilani back as the centre mid for now and go all out for a quality winger and forward.