The Gunners have snapped up Bosnia defender Sead Kolasinac on a free and splashed out £52m on France star Alexandre Lacazette.
The north Londoners are still working hard to complete a deal for Monaco winger Thomas Lemar and are also being linked with a host of other players.
Groves is delighted with Wenger's deals for Kolasinac and Lacazette but believes his old club still needs further reinforcements.
He told Bwin Sport: "I think it's been a successful transfer window.
"We've bought a proven goalscorer in Lacazette who, with the team we have, should be getting at least 20-25 goals this season.
"He looks strong on the ball, with good link up play but is most lethal inside the six yard box, which we've missed for a long time.
"It will take him a while to settle in, with new teammates but he looks physically capable of succeeding.
"Kolasinac is a beast, very strong and creates a lot of chances as we saw in the Emirates Cup.
"There's no doubt there's still work to be done, we need another two players at least – both first team players."
Asked where Wenger should be looking to improve his squad, Groves added: "Arsenal proved with their fourth, fifth or sixth choices [in defence] in the FA Cup final that they can deal with absences at the back.
"Per Mertesacker, Rob Holding and [Nacho] Monreal or Kolasinac can deal with the situation short-term, but then [Shkodran] Mustafi and [Laurent] Koscielny will be back in the fold.
"I do think Arsenal need another centre-half and another top-quality midfielder to help defensively."
