The Frenchman missed out on all his targets, with Roma's Seydou Doumbia opting for Newcastle United, Girondins Bordeaux midfielder Wahbi Khazri heading to Sunderland and Hajduk Split goalkeeper Lovre Kalinic being denied a work permit.
Villa is eight points adrift of safety.
"I am disappointed. I know the team needs strengthening and improving with new players," the manager said. "Probably the main reasons we haven't been able to are that we are bottom of the league and not very attractive for players -- and also because financially speaking the club is not in the situation, probably, where they wanted to spend too much money.
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"One or two new players would have been helpful for the target (of survival). But we still need to believe."
Garde added that he was used to battling adversity and reiterated his commitment to keeping Villa in the Premier League.
"I started my career with disappointment -- not playing for two years because of a cruciate ligament injury. I was 18 at the time and then 18 months later I was playing for the French national team," he said.
"I have a strength inside of me. I will cope with every situation I have to."
(Reporting by Simon Jennings in Bengaluru Editing by Jeremy Gaunt)
