The Reds are expected to dip back into the transfer market this summer.
A memorable 2018-19 campaign saw them challenge for the Premier League title and secure Champions League glory, but Jurgen Klopp is aware of the room for further improvement.
Various positions have been mooted for possible strengthening.
Collymore believes additions in the middle of the park and the final third would be welcome, with Liverpool requiring even greater competition for places while pursuing more major honours.
The ex-Reds striker told The Mirror: “On the pitch, Klopp needs a midfielder who, like Fernandinho at City, will function at 9.8/10 over a season and a striker who will challenge Roberto Firmino on a regular basis, as well as a couple more to flesh out the squad.
“And he will already be thinking about those upgrades.
“Because while City will still be most people’s favourites for the title next season, Klopp has taken his side from being a third of the way to where the Blue Moonies are, to being three-quarters of the way there.
“I’m not sure if that gap will ever close fully, given City’s resources, but there’s no better time for Liverpool to narrow it further than after a Champions League triumph.”
Klopp’s side ended their domestic campaign just a point behind City in the Premier League standings.
Their wait for another top-flight crown is set to reach the 30-year mark, but they have shown themselves to be serious contenders.
The 2019-20 campaign will also see them trying to defend a sixth European Cup crown, with Tottenham having been seen off 2-0 in a showpiece event in Madrid on Saturday.
Big money has been spent to get Liverpool to this point, but more investment is required.
The Reds board have vowed to make funds available, with Klopp also being tipped to be in the market for another goalkeeper – as Simon Mignolet pushes for a move elsewhere – and a creative playmaker, amid talk of a potential move to bring Philippe Coutinho back to Anfield from Barcelona.