National leader Simon Bridges said he hopes to set out his reshuffle early next week, saying it was taking so long because he wanted to ensure he got it right.
During an hour-long interview with Newstalk ZB's Leighton Smith, Bridges said the most important portfolios were different in Opposition compared with Government.
In terms of taking on Labour, National would be targeting, in particular, the portfolio of Regional Development.
"It's an area they can spend a lot of taxpayers' money and not well in my point of view."
Others included Housing because National did not believe Labour could deliver on its promises such as KiwiBuild.
He said Immigration and Industrial Relations were also important portfolios in the next term, because of the reforms planned by Labour.
Earlier he had defended National's record on immigration, saying while he understood the issues for Auckland, businesses needed migration for staff. He said Labour would not be able to meet its promises on housing if it clamped down on immigration.
"They are ones where you say 'actually this Government is doing things we think is taking New Zealand backwards so we need to put strong people in those who are going to be able to draw that out and show what we think is wrong'."
He said one of the factors was who was best suited to go up against the minister on the other side.
Bridges has also said the law and order issue will be one National tackled Labour on as it embarks on considering how to reduce the prison population.
Bridges would not be drawn on the fate of Steven Joyce as Finance spokesman, saying he had "huge experience" and would be offered a good role.
Bridges said he would be following former leader Sir John Key's practice of keeping experience there while bringing fresher talent through.
He hoped the team he set up now would be the team taken into the election, although there could be minor reshuffles if needed.
Bridges also hinted he believed Amy Adams had come second to him in the leadership ballot of the four final contenders, saying while it was a secret ballot "I think you'd have to say Amy Adams had good support there as well".
Earlier in the day, Bridges told RNZ regional development was of interest to him but he was unlikely to take a portfolio himself beyond the National Security area which comes with the job.
The Leader of the Opposition gets briefings by intelligence agencies and is usually on the Intelligence and Security Committee.
The regional development role would pit him against NZ First MP and Regional Development Minister Shane Jones.
"That's something that's important to me, and I think important for New Zealand. But as Leader of the Opposition you have the ability to dip in and out, so it's unlikely I will [take a portfolio]."
Bridges said it would be a "significant" reshuffle but would combine experience with the new.
"It's like making a smoothie. You've got to put the right things in but if you don't do it right, you get it wrong. It doesn't taste good."
Bridges refused to say who might benefit from his reshuffle but told Newshub's AM Show three MPs had impressed him – Bay of Plenty MP Todd Muller, Invercargill MP Sarah Dowie and Kaikoura MP Stuart Smith.
All three are regional MPs and Bridges said all had experience outside Parliament that was valuable in their work as MPs.
Muller was formerly general manager at Zespri and a senior director at Fonterra, Dowie was a lawyer while Smith was a former farmer, winemaker and chair of NZ Winegrowers.