Barker, 22, has signed a three-year deal with the Scottish Premiership club, having been at Preston last term.
The season before, he scored twice in 30 games for Hibernian, while he also had stints with Rotherham United and NAC Breda.
“Last year I didn’t feel we had enough in the final third,” Gerrard said.
“The idea this year was to build a squad with exciting players who can open the door in different ways.”
Rangers have already signed wide players Greg Stewart, Sheyi Ojo, Jordan Jones and Jake Hastie this summer, but have sold Daniel Candeias and Liverpool appear reluctant to allow them to sign Ryan Kent on loan again.
“Jordan Jones and Brandon Barker open the door in one-v-one situations then provide crosses or cut in to score goals. Sheyi Ojo does the same with raw pace and power, Greg Stewart does it in a clever way, while Scott Arfield does it by his running,” added Gerrard.
“I wanted to have everything in our repertoire so that we have enough answers in the final third.”
Barker himself said there was “no better place” for him to develop himself than Rangers.
“It’s a massive club and the name speaks for itself,” Barker told Rangers TV. “The people working here had a massive iNFLuence, too.”
Another Ibrox winger, Glen Middleton, is on the brink of completing a loan move to Hibernian, while Eros Grezda is also likely to leave.
“We’ve had some loan approaches but at the moment the numbers don’t suit the club,” said Gerrard of the Albanian international.
“He’s got two or three loan opportunities that are brewing. It’s a maybe as we sit here right now.”
Gerrard also said Middleton, 19, was “super close” to a move to NAC Breda before Hibs expressed an interest.
“Glen has decided he wants to go to Hibs so that will happen after the weekend,” he explained. “It was his decision.”
Find all the latest football transfers on our dedicated page.